| Message ID | 20200206142812.25989-1-jack@suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | blktrace: Protect q->blk_trace with RCU | expand |
Hi Jan,
What do you think about following patch on the top of yours ?
The new helper that I've added on the top of your patch will also
future uses of the rcu_dereference_protected(). e.g. blktrace
extension [1] support that I'm working on.
P.S. it is compile only if your okay I'll send a separate patch.
+
+/* Dereference q->blk_trace with q->blk_trace_mutex check only. */
+static inline struct blk_trace *blk_trace_rcu_deref(struct
request_queue *q)
+{
+ return rcu_dereference_protected(q->blk_trace,
+
lockdep_is_held(&q->blk_trace_mutex));
+}
/*
* Send out a notify message.
*/
@@ -632,8 +639,7 @@ static int __blk_trace_startstop(struct
request_queue *q, int start)
int ret;
struct blk_trace *bt;
- bt = rcu_dereference_protected(q->blk_trace,
-
lockdep_is_held(&q->blk_trace_mutex));
+ bt = blk_trace_rcu_deref(q);
if (bt == NULL)
return -EINVAL;
@@ -743,8 +749,7 @@ int blk_trace_ioctl(struct block_device *bdev,
unsigned cmd, char __user *arg)
void blk_trace_shutdown(struct request_queue *q)
{
mutex_lock(&q->blk_trace_mutex);
- if (rcu_dereference_protected(q->blk_trace,
-
lockdep_is_held(&q->blk_trace_mutex))) {
+ if (blk_trace_rcu_deref(q)) {
__blk_trace_startstop(q, 0);
__blk_trace_remove(q);
}
@@ -1817,8 +1822,7 @@ static ssize_t sysfs_blk_trace_attr_show(struct
device *dev,
mutex_lock(&q->blk_trace_mutex);
- bt = rcu_dereference_protected(q->blk_trace,
-
lockdep_is_held(&q->blk_trace_mutex));
+ bt = blk_trace_rcu_deref(q);
if (attr == &dev_attr_enable) {
ret = sprintf(buf, "%u\n", !!bt);
goto out_unlock_bdev;
@@ -1881,8 +1885,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct
device *dev,
mutex_lock(&q->blk_trace_mutex);
- bt = rcu_dereference_protected(q->blk_trace,
-
lockdep_is_held(&q->blk_trace_mutex));
+ bt = blk_trace_rcu_deref(q);
if (attr == &dev_attr_enable) {
if (!!value == !!bt) {
ret = 0;
On 02/06/2020 06:28 AM, Jan Kara wrote:
> KASAN is reporting that __blk_add_trace() has a use-after-free issue
> when accessing q->blk_trace. Indeed the switching of block tracing (and
> thus eventual freeing of q->blk_trace) is completely unsynchronized with
> the currently running tracing and thus it can happen that the blk_trace
> structure is being freed just while __blk_add_trace() works on it.
> Protect accesses to q->blk_trace by RCU during tracing and make sure we
> wait for the end of RCU grace period when shutting down tracing. Luckily
> that is rare enough event that we can afford that. Note that postponing
> the freeing of blk_trace to an RCU callback should better be avoided as
> it could have unexpected user visible side-effects as debugfs files
> would be still existing for a short while block tracing has been shut
> down.
>
> Link:https://bugzilla.kernel.org/show_bug.cgi?id=205711
> CC:stable@vger.kernel.org
> Reported-by: Tristan<tristmd@gmail.com>
> Signed-off-by: Jan Kara<jack@suse.cz>
> ---
[1] https://marc.info/?l=linux-btrace&m=157422391521376&w=2
On 2/6/20 11:46 AM, Chaitanya Kulkarni wrote: > Hi Jan, > > What do you think about following patch on the top of yours ? > > The new helper that I've added on the top of your patch will also > future uses of the rcu_dereference_protected(). e.g. blktrace > extension [1] support that I'm working on. > > P.S. it is compile only if your okay I'll send a separate patch. > > + > +/* Dereference q->blk_trace with q->blk_trace_mutex check only. */ > +static inline struct blk_trace *blk_trace_rcu_deref(struct > request_queue *q) > +{ > + return rcu_dereference_protected(q->blk_trace, > + > lockdep_is_held(&q->blk_trace_mutex)); > +} Let's please not do that, it serves no real purpose and it just obfuscates what's really going on.
On 02/06/2020 10:49 AM, Jens Axboe wrote: > Let's please not do that, it serves no real purpose and it just > obfuscates what's really going on. > > -- Jens Axboe Okay, will avoid such changes and comments in future. Thanks Jens for the clarification.
Looks good. Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> On 02/06/2020 06:28 AM, Jan Kara wrote: > KASAN is reporting that __blk_add_trace() has a use-after-free issue > when accessing q->blk_trace. Indeed the switching of block tracing (and > thus eventual freeing of q->blk_trace) is completely unsynchronized with > the currently running tracing and thus it can happen that the blk_trace > structure is being freed just while __blk_add_trace() works on it. > Protect accesses to q->blk_trace by RCU during tracing and make sure we > wait for the end of RCU grace period when shutting down tracing. Luckily > that is rare enough event that we can afford that. Note that postponing > the freeing of blk_trace to an RCU callback should better be avoided as > it could have unexpected user visible side-effects as debugfs files > would be still existing for a short while block tracing has been shut > down. > > Link:https://bugzilla.kernel.org/show_bug.cgi?id=205711 > CC:stable@vger.kernel.org > Reported-by: Tristan<tristmd@gmail.com> > Signed-off-by: Jan Kara<jack@suse.cz>
On Thu, Feb 6, 2020 at 10:29 PM Jan Kara <jack@suse.cz> wrote: > > KASAN is reporting that __blk_add_trace() has a use-after-free issue > when accessing q->blk_trace. Indeed the switching of block tracing (and > thus eventual freeing of q->blk_trace) is completely unsynchronized with > the currently running tracing and thus it can happen that the blk_trace > structure is being freed just while __blk_add_trace() works on it. > Protect accesses to q->blk_trace by RCU during tracing and make sure we > wait for the end of RCU grace period when shutting down tracing. Luckily > that is rare enough event that we can afford that. Note that postponing > the freeing of blk_trace to an RCU callback should better be avoided as > it could have unexpected user visible side-effects as debugfs files > would be still existing for a short while block tracing has been shut > down. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=205711 > CC: stable@vger.kernel.org > Reported-by: Tristan <tristmd@gmail.com> > Signed-off-by: Jan Kara <jack@suse.cz> > --- > include/linux/blkdev.h | 2 +- > include/linux/blktrace_api.h | 18 +++++-- > kernel/trace/blktrace.c | 114 +++++++++++++++++++++++++++++++------------ > 3 files changed, 97 insertions(+), 37 deletions(-) > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index 4c636c42ad68..1cb5afed5515 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -524,7 +524,7 @@ struct request_queue { > unsigned int sg_reserved_size; > int node; > #ifdef CONFIG_BLK_DEV_IO_TRACE > - struct blk_trace *blk_trace; > + struct blk_trace __rcu *blk_trace; > struct mutex blk_trace_mutex; > #endif > /* > diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h > index 7bb2d8de9f30..3b6ff5902edc 100644 > --- a/include/linux/blktrace_api.h > +++ b/include/linux/blktrace_api.h > @@ -51,9 +51,13 @@ void __trace_note_message(struct blk_trace *, struct blkcg *blkcg, const char *f > **/ > #define blk_add_cgroup_trace_msg(q, cg, fmt, ...) \ > do { \ > - struct blk_trace *bt = (q)->blk_trace; \ > + struct blk_trace *bt; \ > + \ > + rcu_read_lock(); \ > + bt = rcu_dereference((q)->blk_trace); \ > if (unlikely(bt)) \ > __trace_note_message(bt, cg, fmt, ##__VA_ARGS__);\ > + rcu_read_unlock(); \ > } while (0) > #define blk_add_trace_msg(q, fmt, ...) \ > blk_add_cgroup_trace_msg(q, NULL, fmt, ##__VA_ARGS__) > @@ -61,10 +65,14 @@ void __trace_note_message(struct blk_trace *, struct blkcg *blkcg, const char *f > > static inline bool blk_trace_note_message_enabled(struct request_queue *q) > { > - struct blk_trace *bt = q->blk_trace; > - if (likely(!bt)) > - return false; > - return bt->act_mask & BLK_TC_NOTIFY; > + struct blk_trace *bt; > + bool ret; > + > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > + ret = bt && (bt->act_mask & BLK_TC_NOTIFY); > + rcu_read_unlock(); > + return ret; > } > > extern void blk_add_driver_data(struct request_queue *q, struct request *rq, > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c > index 475e29498bca..a6d3016410eb 100644 > --- a/kernel/trace/blktrace.c > +++ b/kernel/trace/blktrace.c > @@ -335,6 +335,7 @@ static void put_probe_ref(void) > > static void blk_trace_cleanup(struct blk_trace *bt) > { > + synchronize_rcu(); > blk_trace_free(bt); > put_probe_ref(); > } > @@ -629,8 +630,10 @@ static int compat_blk_trace_setup(struct request_queue *q, char *name, > static int __blk_trace_startstop(struct request_queue *q, int start) > { > int ret; > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + bt = rcu_dereference_protected(q->blk_trace, > + lockdep_is_held(&q->blk_trace_mutex)); > if (bt == NULL) > return -EINVAL; > > @@ -740,8 +743,8 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg) > void blk_trace_shutdown(struct request_queue *q) > { > mutex_lock(&q->blk_trace_mutex); > - > - if (q->blk_trace) { > + if (rcu_dereference_protected(q->blk_trace, > + lockdep_is_held(&q->blk_trace_mutex))) { > __blk_trace_startstop(q, 0); > __blk_trace_remove(q); > } > @@ -752,8 +755,10 @@ void blk_trace_shutdown(struct request_queue *q) > #ifdef CONFIG_BLK_CGROUP > static u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + /* We don't use the 'bt' value here except as an optimization... */ > + bt = rcu_dereference_protected(q->blk_trace, 1); > if (!bt || !(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP)) > return 0; > > @@ -796,10 +801,14 @@ blk_trace_request_get_cgid(struct request_queue *q, struct request *rq) > static void blk_add_trace_rq(struct request *rq, int error, > unsigned int nr_bytes, u32 what, u64 cgid) > { > - struct blk_trace *bt = rq->q->blk_trace; > + struct blk_trace *bt; > > - if (likely(!bt)) > + rcu_read_lock(); > + bt = rcu_dereference(rq->q->blk_trace); > + if (likely(!bt)) { > + rcu_read_unlock(); > return; > + } > > if (blk_rq_is_passthrough(rq)) > what |= BLK_TC_ACT(BLK_TC_PC); > @@ -808,6 +817,7 @@ static void blk_add_trace_rq(struct request *rq, int error, > > __blk_add_trace(bt, blk_rq_trace_sector(rq), nr_bytes, req_op(rq), > rq->cmd_flags, what, error, 0, NULL, cgid); > + rcu_read_unlock(); > } > > static void blk_add_trace_rq_insert(void *ignore, > @@ -853,14 +863,19 @@ static void blk_add_trace_rq_complete(void *ignore, struct request *rq, > static void blk_add_trace_bio(struct request_queue *q, struct bio *bio, > u32 what, int error) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > - if (likely(!bt)) > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > + if (likely(!bt)) { > + rcu_read_unlock(); > return; > + } > > __blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size, > bio_op(bio), bio->bi_opf, what, error, 0, NULL, > blk_trace_bio_get_cgid(q, bio)); > + rcu_read_unlock(); > } > > static void blk_add_trace_bio_bounce(void *ignore, > @@ -905,11 +920,14 @@ static void blk_add_trace_getrq(void *ignore, > if (bio) > blk_add_trace_bio(q, bio, BLK_TA_GETRQ, 0); > else { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > if (bt) > __blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_GETRQ, 0, 0, > NULL, 0); > + rcu_read_unlock(); > } > } > > @@ -921,27 +939,35 @@ static void blk_add_trace_sleeprq(void *ignore, > if (bio) > blk_add_trace_bio(q, bio, BLK_TA_SLEEPRQ, 0); > else { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > if (bt) > __blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_SLEEPRQ, > 0, 0, NULL, 0); > + rcu_read_unlock(); > } > } > > static void blk_add_trace_plug(void *ignore, struct request_queue *q) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > if (bt) > __blk_add_trace(bt, 0, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL, 0); > + rcu_read_unlock(); > } > > static void blk_add_trace_unplug(void *ignore, struct request_queue *q, > unsigned int depth, bool explicit) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > if (bt) { > __be64 rpdu = cpu_to_be64(depth); > u32 what; > @@ -953,14 +979,17 @@ static void blk_add_trace_unplug(void *ignore, struct request_queue *q, > > __blk_add_trace(bt, 0, 0, 0, 0, what, 0, sizeof(rpdu), &rpdu, 0); > } > + rcu_read_unlock(); > } > > static void blk_add_trace_split(void *ignore, > struct request_queue *q, struct bio *bio, > unsigned int pdu) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > if (bt) { > __be64 rpdu = cpu_to_be64(pdu); > > @@ -969,6 +998,7 @@ static void blk_add_trace_split(void *ignore, > BLK_TA_SPLIT, bio->bi_status, sizeof(rpdu), > &rpdu, blk_trace_bio_get_cgid(q, bio)); > } > + rcu_read_unlock(); > } > > /** > @@ -988,11 +1018,15 @@ static void blk_add_trace_bio_remap(void *ignore, > struct request_queue *q, struct bio *bio, > dev_t dev, sector_t from) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > struct blk_io_trace_remap r; > > - if (likely(!bt)) > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > + if (likely(!bt)) { > + rcu_read_unlock(); > return; > + } > > r.device_from = cpu_to_be32(dev); > r.device_to = cpu_to_be32(bio_dev(bio)); > @@ -1001,6 +1035,7 @@ static void blk_add_trace_bio_remap(void *ignore, > __blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size, > bio_op(bio), bio->bi_opf, BLK_TA_REMAP, bio->bi_status, > sizeof(r), &r, blk_trace_bio_get_cgid(q, bio)); > + rcu_read_unlock(); > } > > /** > @@ -1021,11 +1056,15 @@ static void blk_add_trace_rq_remap(void *ignore, > struct request *rq, dev_t dev, > sector_t from) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > struct blk_io_trace_remap r; > > - if (likely(!bt)) > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > + if (likely(!bt)) { > + rcu_read_unlock(); > return; > + } > > r.device_from = cpu_to_be32(dev); > r.device_to = cpu_to_be32(disk_devt(rq->rq_disk)); > @@ -1034,6 +1073,7 @@ static void blk_add_trace_rq_remap(void *ignore, > __blk_add_trace(bt, blk_rq_pos(rq), blk_rq_bytes(rq), > rq_data_dir(rq), 0, BLK_TA_REMAP, 0, > sizeof(r), &r, blk_trace_request_get_cgid(q, rq)); > + rcu_read_unlock(); > } > > /** > @@ -1051,14 +1091,19 @@ void blk_add_driver_data(struct request_queue *q, > struct request *rq, > void *data, size_t len) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > - if (likely(!bt)) > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > + if (likely(!bt)) { > + rcu_read_unlock(); > return; > + } > > __blk_add_trace(bt, blk_rq_trace_sector(rq), blk_rq_bytes(rq), 0, 0, > BLK_TA_DRV_DATA, 0, len, data, > blk_trace_request_get_cgid(q, rq)); > + rcu_read_unlock(); > } > EXPORT_SYMBOL_GPL(blk_add_driver_data); > > @@ -1597,6 +1642,7 @@ static int blk_trace_remove_queue(struct request_queue *q) > return -EINVAL; > > put_probe_ref(); > + synchronize_rcu(); > blk_trace_free(bt); > return 0; > } > @@ -1758,6 +1804,7 @@ static ssize_t sysfs_blk_trace_attr_show(struct device *dev, > struct hd_struct *p = dev_to_part(dev); > struct request_queue *q; > struct block_device *bdev; > + struct blk_trace *bt; > ssize_t ret = -ENXIO; > > bdev = bdget(part_devt(p)); > @@ -1770,21 +1817,23 @@ static ssize_t sysfs_blk_trace_attr_show(struct device *dev, > > mutex_lock(&q->blk_trace_mutex); > > + bt = rcu_dereference_protected(q->blk_trace, > + lockdep_is_held(&q->blk_trace_mutex)); > if (attr == &dev_attr_enable) { > - ret = sprintf(buf, "%u\n", !!q->blk_trace); > + ret = sprintf(buf, "%u\n", !!bt); > goto out_unlock_bdev; > } > > - if (q->blk_trace == NULL) > + if (bt == NULL) > ret = sprintf(buf, "disabled\n"); > else if (attr == &dev_attr_act_mask) > - ret = blk_trace_mask2str(buf, q->blk_trace->act_mask); > + ret = blk_trace_mask2str(buf, bt->act_mask); > else if (attr == &dev_attr_pid) > - ret = sprintf(buf, "%u\n", q->blk_trace->pid); > + ret = sprintf(buf, "%u\n", bt->pid); > else if (attr == &dev_attr_start_lba) > - ret = sprintf(buf, "%llu\n", q->blk_trace->start_lba); > + ret = sprintf(buf, "%llu\n", bt->start_lba); > else if (attr == &dev_attr_end_lba) > - ret = sprintf(buf, "%llu\n", q->blk_trace->end_lba); > + ret = sprintf(buf, "%llu\n", bt->end_lba); > > out_unlock_bdev: > mutex_unlock(&q->blk_trace_mutex); > @@ -1801,6 +1850,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, > struct block_device *bdev; > struct request_queue *q; > struct hd_struct *p; > + struct blk_trace *bt; > u64 value; > ssize_t ret = -EINVAL; > > @@ -1831,8 +1881,10 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, > > mutex_lock(&q->blk_trace_mutex); > > + bt = rcu_dereference_protected(q->blk_trace, > + lockdep_is_held(&q->blk_trace_mutex)); > if (attr == &dev_attr_enable) { > - if (!!value == !!q->blk_trace) { > + if (!!value == !!bt) { > ret = 0; > goto out_unlock_bdev; > } > @@ -1844,18 +1896,18 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, > } > > ret = 0; > - if (q->blk_trace == NULL) > + if (bt == NULL) > ret = blk_trace_setup_queue(q, bdev); > > if (ret == 0) { > if (attr == &dev_attr_act_mask) > - q->blk_trace->act_mask = value; > + bt->act_mask = value; > else if (attr == &dev_attr_pid) > - q->blk_trace->pid = value; > + bt->pid = value; > else if (attr == &dev_attr_start_lba) > - q->blk_trace->start_lba = value; > + bt->start_lba = value; > else if (attr == &dev_attr_end_lba) > - q->blk_trace->end_lba = value; > + bt->end_lba = value; > } > > out_unlock_bdev: > -- > 2.16.4 > Looks fine: Reviewed-by: Ming Lei <ming.lei@redhat.com>
On 2020-02-06 06:28, Jan Kara wrote: > KASAN is reporting that __blk_add_trace() has a use-after-free issue > when accessing q->blk_trace. Indeed the switching of block tracing (and > thus eventual freeing of q->blk_trace) is completely unsynchronized with > the currently running tracing and thus it can happen that the blk_trace > structure is being freed just while __blk_add_trace() works on it. > Protect accesses to q->blk_trace by RCU during tracing and make sure we > wait for the end of RCU grace period when shutting down tracing. Luckily > that is rare enough event that we can afford that. Note that postponing > the freeing of blk_trace to an RCU callback should better be avoided as > it could have unexpected user visible side-effects as debugfs files > would be still existing for a short while block tracing has been shut > down. Reviewed-by: Bart Van Assche <bvanassche@acm.org>
On Thu 06-02-20 15:28:12, Jan Kara wrote: > KASAN is reporting that __blk_add_trace() has a use-after-free issue > when accessing q->blk_trace. Indeed the switching of block tracing (and > thus eventual freeing of q->blk_trace) is completely unsynchronized with > the currently running tracing and thus it can happen that the blk_trace > structure is being freed just while __blk_add_trace() works on it. > Protect accesses to q->blk_trace by RCU during tracing and make sure we > wait for the end of RCU grace period when shutting down tracing. Luckily > that is rare enough event that we can afford that. Note that postponing > the freeing of blk_trace to an RCU callback should better be avoided as > it could have unexpected user visible side-effects as debugfs files > would be still existing for a short while block tracing has been shut > down. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=205711 > CC: stable@vger.kernel.org > Reported-by: Tristan <tristmd@gmail.com> > Signed-off-by: Jan Kara <jack@suse.cz> Jens, do you plan to pick up the patch? Also the reporter asked me to update the reference as: Reported-by: Tristan Madani <tristmd@gmail.com> Should I resend the patch with this update & reviewed-by's or will you fix it up on commit? Thanks. Honza > --- > include/linux/blkdev.h | 2 +- > include/linux/blktrace_api.h | 18 +++++-- > kernel/trace/blktrace.c | 114 +++++++++++++++++++++++++++++++------------ > 3 files changed, 97 insertions(+), 37 deletions(-) > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index 4c636c42ad68..1cb5afed5515 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -524,7 +524,7 @@ struct request_queue { > unsigned int sg_reserved_size; > int node; > #ifdef CONFIG_BLK_DEV_IO_TRACE > - struct blk_trace *blk_trace; > + struct blk_trace __rcu *blk_trace; > struct mutex blk_trace_mutex; > #endif > /* > diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h > index 7bb2d8de9f30..3b6ff5902edc 100644 > --- a/include/linux/blktrace_api.h > +++ b/include/linux/blktrace_api.h > @@ -51,9 +51,13 @@ void __trace_note_message(struct blk_trace *, struct blkcg *blkcg, const char *f > **/ > #define blk_add_cgroup_trace_msg(q, cg, fmt, ...) \ > do { \ > - struct blk_trace *bt = (q)->blk_trace; \ > + struct blk_trace *bt; \ > + \ > + rcu_read_lock(); \ > + bt = rcu_dereference((q)->blk_trace); \ > if (unlikely(bt)) \ > __trace_note_message(bt, cg, fmt, ##__VA_ARGS__);\ > + rcu_read_unlock(); \ > } while (0) > #define blk_add_trace_msg(q, fmt, ...) \ > blk_add_cgroup_trace_msg(q, NULL, fmt, ##__VA_ARGS__) > @@ -61,10 +65,14 @@ void __trace_note_message(struct blk_trace *, struct blkcg *blkcg, const char *f > > static inline bool blk_trace_note_message_enabled(struct request_queue *q) > { > - struct blk_trace *bt = q->blk_trace; > - if (likely(!bt)) > - return false; > - return bt->act_mask & BLK_TC_NOTIFY; > + struct blk_trace *bt; > + bool ret; > + > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > + ret = bt && (bt->act_mask & BLK_TC_NOTIFY); > + rcu_read_unlock(); > + return ret; > } > > extern void blk_add_driver_data(struct request_queue *q, struct request *rq, > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c > index 475e29498bca..a6d3016410eb 100644 > --- a/kernel/trace/blktrace.c > +++ b/kernel/trace/blktrace.c > @@ -335,6 +335,7 @@ static void put_probe_ref(void) > > static void blk_trace_cleanup(struct blk_trace *bt) > { > + synchronize_rcu(); > blk_trace_free(bt); > put_probe_ref(); > } > @@ -629,8 +630,10 @@ static int compat_blk_trace_setup(struct request_queue *q, char *name, > static int __blk_trace_startstop(struct request_queue *q, int start) > { > int ret; > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + bt = rcu_dereference_protected(q->blk_trace, > + lockdep_is_held(&q->blk_trace_mutex)); > if (bt == NULL) > return -EINVAL; > > @@ -740,8 +743,8 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg) > void blk_trace_shutdown(struct request_queue *q) > { > mutex_lock(&q->blk_trace_mutex); > - > - if (q->blk_trace) { > + if (rcu_dereference_protected(q->blk_trace, > + lockdep_is_held(&q->blk_trace_mutex))) { > __blk_trace_startstop(q, 0); > __blk_trace_remove(q); > } > @@ -752,8 +755,10 @@ void blk_trace_shutdown(struct request_queue *q) > #ifdef CONFIG_BLK_CGROUP > static u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + /* We don't use the 'bt' value here except as an optimization... */ > + bt = rcu_dereference_protected(q->blk_trace, 1); > if (!bt || !(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP)) > return 0; > > @@ -796,10 +801,14 @@ blk_trace_request_get_cgid(struct request_queue *q, struct request *rq) > static void blk_add_trace_rq(struct request *rq, int error, > unsigned int nr_bytes, u32 what, u64 cgid) > { > - struct blk_trace *bt = rq->q->blk_trace; > + struct blk_trace *bt; > > - if (likely(!bt)) > + rcu_read_lock(); > + bt = rcu_dereference(rq->q->blk_trace); > + if (likely(!bt)) { > + rcu_read_unlock(); > return; > + } > > if (blk_rq_is_passthrough(rq)) > what |= BLK_TC_ACT(BLK_TC_PC); > @@ -808,6 +817,7 @@ static void blk_add_trace_rq(struct request *rq, int error, > > __blk_add_trace(bt, blk_rq_trace_sector(rq), nr_bytes, req_op(rq), > rq->cmd_flags, what, error, 0, NULL, cgid); > + rcu_read_unlock(); > } > > static void blk_add_trace_rq_insert(void *ignore, > @@ -853,14 +863,19 @@ static void blk_add_trace_rq_complete(void *ignore, struct request *rq, > static void blk_add_trace_bio(struct request_queue *q, struct bio *bio, > u32 what, int error) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > - if (likely(!bt)) > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > + if (likely(!bt)) { > + rcu_read_unlock(); > return; > + } > > __blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size, > bio_op(bio), bio->bi_opf, what, error, 0, NULL, > blk_trace_bio_get_cgid(q, bio)); > + rcu_read_unlock(); > } > > static void blk_add_trace_bio_bounce(void *ignore, > @@ -905,11 +920,14 @@ static void blk_add_trace_getrq(void *ignore, > if (bio) > blk_add_trace_bio(q, bio, BLK_TA_GETRQ, 0); > else { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > if (bt) > __blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_GETRQ, 0, 0, > NULL, 0); > + rcu_read_unlock(); > } > } > > @@ -921,27 +939,35 @@ static void blk_add_trace_sleeprq(void *ignore, > if (bio) > blk_add_trace_bio(q, bio, BLK_TA_SLEEPRQ, 0); > else { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > if (bt) > __blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_SLEEPRQ, > 0, 0, NULL, 0); > + rcu_read_unlock(); > } > } > > static void blk_add_trace_plug(void *ignore, struct request_queue *q) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > if (bt) > __blk_add_trace(bt, 0, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL, 0); > + rcu_read_unlock(); > } > > static void blk_add_trace_unplug(void *ignore, struct request_queue *q, > unsigned int depth, bool explicit) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > if (bt) { > __be64 rpdu = cpu_to_be64(depth); > u32 what; > @@ -953,14 +979,17 @@ static void blk_add_trace_unplug(void *ignore, struct request_queue *q, > > __blk_add_trace(bt, 0, 0, 0, 0, what, 0, sizeof(rpdu), &rpdu, 0); > } > + rcu_read_unlock(); > } > > static void blk_add_trace_split(void *ignore, > struct request_queue *q, struct bio *bio, > unsigned int pdu) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > if (bt) { > __be64 rpdu = cpu_to_be64(pdu); > > @@ -969,6 +998,7 @@ static void blk_add_trace_split(void *ignore, > BLK_TA_SPLIT, bio->bi_status, sizeof(rpdu), > &rpdu, blk_trace_bio_get_cgid(q, bio)); > } > + rcu_read_unlock(); > } > > /** > @@ -988,11 +1018,15 @@ static void blk_add_trace_bio_remap(void *ignore, > struct request_queue *q, struct bio *bio, > dev_t dev, sector_t from) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > struct blk_io_trace_remap r; > > - if (likely(!bt)) > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > + if (likely(!bt)) { > + rcu_read_unlock(); > return; > + } > > r.device_from = cpu_to_be32(dev); > r.device_to = cpu_to_be32(bio_dev(bio)); > @@ -1001,6 +1035,7 @@ static void blk_add_trace_bio_remap(void *ignore, > __blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size, > bio_op(bio), bio->bi_opf, BLK_TA_REMAP, bio->bi_status, > sizeof(r), &r, blk_trace_bio_get_cgid(q, bio)); > + rcu_read_unlock(); > } > > /** > @@ -1021,11 +1056,15 @@ static void blk_add_trace_rq_remap(void *ignore, > struct request *rq, dev_t dev, > sector_t from) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > struct blk_io_trace_remap r; > > - if (likely(!bt)) > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > + if (likely(!bt)) { > + rcu_read_unlock(); > return; > + } > > r.device_from = cpu_to_be32(dev); > r.device_to = cpu_to_be32(disk_devt(rq->rq_disk)); > @@ -1034,6 +1073,7 @@ static void blk_add_trace_rq_remap(void *ignore, > __blk_add_trace(bt, blk_rq_pos(rq), blk_rq_bytes(rq), > rq_data_dir(rq), 0, BLK_TA_REMAP, 0, > sizeof(r), &r, blk_trace_request_get_cgid(q, rq)); > + rcu_read_unlock(); > } > > /** > @@ -1051,14 +1091,19 @@ void blk_add_driver_data(struct request_queue *q, > struct request *rq, > void *data, size_t len) > { > - struct blk_trace *bt = q->blk_trace; > + struct blk_trace *bt; > > - if (likely(!bt)) > + rcu_read_lock(); > + bt = rcu_dereference(q->blk_trace); > + if (likely(!bt)) { > + rcu_read_unlock(); > return; > + } > > __blk_add_trace(bt, blk_rq_trace_sector(rq), blk_rq_bytes(rq), 0, 0, > BLK_TA_DRV_DATA, 0, len, data, > blk_trace_request_get_cgid(q, rq)); > + rcu_read_unlock(); > } > EXPORT_SYMBOL_GPL(blk_add_driver_data); > > @@ -1597,6 +1642,7 @@ static int blk_trace_remove_queue(struct request_queue *q) > return -EINVAL; > > put_probe_ref(); > + synchronize_rcu(); > blk_trace_free(bt); > return 0; > } > @@ -1758,6 +1804,7 @@ static ssize_t sysfs_blk_trace_attr_show(struct device *dev, > struct hd_struct *p = dev_to_part(dev); > struct request_queue *q; > struct block_device *bdev; > + struct blk_trace *bt; > ssize_t ret = -ENXIO; > > bdev = bdget(part_devt(p)); > @@ -1770,21 +1817,23 @@ static ssize_t sysfs_blk_trace_attr_show(struct device *dev, > > mutex_lock(&q->blk_trace_mutex); > > + bt = rcu_dereference_protected(q->blk_trace, > + lockdep_is_held(&q->blk_trace_mutex)); > if (attr == &dev_attr_enable) { > - ret = sprintf(buf, "%u\n", !!q->blk_trace); > + ret = sprintf(buf, "%u\n", !!bt); > goto out_unlock_bdev; > } > > - if (q->blk_trace == NULL) > + if (bt == NULL) > ret = sprintf(buf, "disabled\n"); > else if (attr == &dev_attr_act_mask) > - ret = blk_trace_mask2str(buf, q->blk_trace->act_mask); > + ret = blk_trace_mask2str(buf, bt->act_mask); > else if (attr == &dev_attr_pid) > - ret = sprintf(buf, "%u\n", q->blk_trace->pid); > + ret = sprintf(buf, "%u\n", bt->pid); > else if (attr == &dev_attr_start_lba) > - ret = sprintf(buf, "%llu\n", q->blk_trace->start_lba); > + ret = sprintf(buf, "%llu\n", bt->start_lba); > else if (attr == &dev_attr_end_lba) > - ret = sprintf(buf, "%llu\n", q->blk_trace->end_lba); > + ret = sprintf(buf, "%llu\n", bt->end_lba); > > out_unlock_bdev: > mutex_unlock(&q->blk_trace_mutex); > @@ -1801,6 +1850,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, > struct block_device *bdev; > struct request_queue *q; > struct hd_struct *p; > + struct blk_trace *bt; > u64 value; > ssize_t ret = -EINVAL; > > @@ -1831,8 +1881,10 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, > > mutex_lock(&q->blk_trace_mutex); > > + bt = rcu_dereference_protected(q->blk_trace, > + lockdep_is_held(&q->blk_trace_mutex)); > if (attr == &dev_attr_enable) { > - if (!!value == !!q->blk_trace) { > + if (!!value == !!bt) { > ret = 0; > goto out_unlock_bdev; > } > @@ -1844,18 +1896,18 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, > } > > ret = 0; > - if (q->blk_trace == NULL) > + if (bt == NULL) > ret = blk_trace_setup_queue(q, bdev); > > if (ret == 0) { > if (attr == &dev_attr_act_mask) > - q->blk_trace->act_mask = value; > + bt->act_mask = value; > else if (attr == &dev_attr_pid) > - q->blk_trace->pid = value; > + bt->pid = value; > else if (attr == &dev_attr_start_lba) > - q->blk_trace->start_lba = value; > + bt->start_lba = value; > else if (attr == &dev_attr_end_lba) > - q->blk_trace->end_lba = value; > + bt->end_lba = value; > } > > out_unlock_bdev: > -- > 2.16.4 >
On Wed, Feb 19, 2020 at 01:59:47PM +0100, Jan Kara wrote: > On Thu 06-02-20 15:28:12, Jan Kara wrote: > > KASAN is reporting that __blk_add_trace() has a use-after-free issue > > when accessing q->blk_trace. Indeed the switching of block tracing (and > > thus eventual freeing of q->blk_trace) is completely unsynchronized with > > the currently running tracing and thus it can happen that the blk_trace > > structure is being freed just while __blk_add_trace() works on it. > > Protect accesses to q->blk_trace by RCU during tracing and make sure we > > wait for the end of RCU grace period when shutting down tracing. Luckily > > that is rare enough event that we can afford that. Note that postponing > > the freeing of blk_trace to an RCU callback should better be avoided as > > it could have unexpected user visible side-effects as debugfs files > > would be still existing for a short while block tracing has been shut > > down. > > > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=205711 > > CC: stable@vger.kernel.org > > Reported-by: Tristan <tristmd@gmail.com> > > Signed-off-by: Jan Kara <jack@suse.cz> > > Jens, do you plan to pick up the patch? Also the reporter asked me to > update the reference as: > > Reported-by: Tristan Madani <tristmd@gmail.com> > > Should I resend the patch with this update & reviewed-by's or will you fix > it up on commit? Thanks. > I have run concurrent quick/repeated blktrace & long-time heavy IO, looks this patch just works fine, so: Tested-by: Ming Lei <ming.lei@redhat.com> Jens, any chance to take a look at this CVE issue? Thanks, Ming
On 2/25/20 3:20 AM, Ming Lei wrote: > On Wed, Feb 19, 2020 at 01:59:47PM +0100, Jan Kara wrote: >> On Thu 06-02-20 15:28:12, Jan Kara wrote: >>> KASAN is reporting that __blk_add_trace() has a use-after-free issue >>> when accessing q->blk_trace. Indeed the switching of block tracing (and >>> thus eventual freeing of q->blk_trace) is completely unsynchronized with >>> the currently running tracing and thus it can happen that the blk_trace >>> structure is being freed just while __blk_add_trace() works on it. >>> Protect accesses to q->blk_trace by RCU during tracing and make sure we >>> wait for the end of RCU grace period when shutting down tracing. Luckily >>> that is rare enough event that we can afford that. Note that postponing >>> the freeing of blk_trace to an RCU callback should better be avoided as >>> it could have unexpected user visible side-effects as debugfs files >>> would be still existing for a short while block tracing has been shut >>> down. >>> >>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=205711 >>> CC: stable@vger.kernel.org >>> Reported-by: Tristan <tristmd@gmail.com> >>> Signed-off-by: Jan Kara <jack@suse.cz> >> >> Jens, do you plan to pick up the patch? Also the reporter asked me to >> update the reference as: >> >> Reported-by: Tristan Madani <tristmd@gmail.com> >> >> Should I resend the patch with this update & reviewed-by's or will you fix >> it up on commit? Thanks. >> > > I have run concurrent quick/repeated blktrace & long-time heavy IO, looks > this patch just works fine, so: > > Tested-by: Ming Lei <ming.lei@redhat.com> > > Jens, any chance to take a look at this CVE issue? Queued up for 5.6, thanks everyone.
On Thu, Feb 06, 2020 at 03:28:12PM +0100, Jan Kara wrote: > @@ -1844,18 +1896,18 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, > } > > ret = 0; > - if (q->blk_trace == NULL) > + if (bt == NULL) > ret = blk_trace_setup_queue(q, bdev); > > if (ret == 0) { > if (attr == &dev_attr_act_mask) > - q->blk_trace->act_mask = value; > + bt->act_mask = value; You've likely seen this already, but Coverity complains that "bt" may be a NULL pointer here, since we checked it for NULL above. CID 1460458: Null pointer dereferences (FORWARD_NULL) > else if (attr == &dev_attr_pid) > - q->blk_trace->pid = value; > + bt->pid = value; > else if (attr == &dev_attr_start_lba) > - q->blk_trace->start_lba = value; > + bt->start_lba = value; > else if (attr == &dev_attr_end_lba) > - q->blk_trace->end_lba = value; > + bt->end_lba = value; > } > > out_unlock_bdev: >
By any chance will the following patch be able to get rid of
the warning ?
index 4560878f0bac..889555910555 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -1895,9 +1895,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct
device *dev,
goto out_unlock_bdev;
}
- ret = 0;
- if (bt == NULL)
- ret = blk_trace_setup_queue(q, bdev);
+ ret = bt == NULL ? blk_trace_setup_queue(q, bdev) : 0;
if (ret == 0) {
if (attr == &dev_attr_act_mask)
On 03/02/2020 12:41 PM, Bjorn Helgaas wrote:
> On Thu, Feb 06, 2020 at 03:28:12PM +0100, Jan Kara wrote:
>
>> @@ -1844,18 +1896,18 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
>> }
>>
>> ret = 0;
>> - if (q->blk_trace == NULL)
>> + if (bt == NULL)
>> ret = blk_trace_setup_queue(q, bdev);
>>
>> if (ret == 0) {
>> if (attr == &dev_attr_act_mask)
>> - q->blk_trace->act_mask = value;
>> + bt->act_mask = value;
>
> You've likely seen this already, but Coverity complains that "bt" may
> be a NULL pointer here, since we checked it for NULL above.
>
> CID 1460458: Null pointer dereferences (FORWARD_NULL)
>
>> else if (attr == &dev_attr_pid)
>> - q->blk_trace->pid = value;
>> + bt->pid = value;
>> else if (attr == &dev_attr_start_lba)
>> - q->blk_trace->start_lba = value;
>> + bt->start_lba = value;
>> else if (attr == &dev_attr_end_lba)
>> - q->blk_trace->end_lba = value;
>> + bt->end_lba = value;
>> }
>>
>> out_unlock_bdev:
>>
>
On Mon, Mar 02, 2020 at 09:19:33PM +0000, Chaitanya Kulkarni wrote: > By any chance will the following patch be able to get rid of > the warning ? > > index 4560878f0bac..889555910555 100644 > --- a/kernel/trace/blktrace.c > +++ b/kernel/trace/blktrace.c > @@ -1895,9 +1895,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct > device *dev, > goto out_unlock_bdev; > } > > - ret = 0; > - if (bt == NULL) > - ret = blk_trace_setup_queue(q, bdev); > + ret = bt == NULL ? blk_trace_setup_queue(q, bdev) : 0; > > if (ret == 0) { > if (attr == &dev_attr_act_mask) I don't have a way to run Coverity (I just get periodic reports), but I don't see the point of this patch. I assume "bt" can still be NULL (otherwise there'd be no point in testing it) and we still reference "bt->pid" below. > On 03/02/2020 12:41 PM, Bjorn Helgaas wrote: > > On Thu, Feb 06, 2020 at 03:28:12PM +0100, Jan Kara wrote: > > > >> @@ -1844,18 +1896,18 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, > >> } > >> > >> ret = 0; > >> - if (q->blk_trace == NULL) > >> + if (bt == NULL) > >> ret = blk_trace_setup_queue(q, bdev); > >> > >> if (ret == 0) { > >> if (attr == &dev_attr_act_mask) > >> - q->blk_trace->act_mask = value; > >> + bt->act_mask = value; > > > > You've likely seen this already, but Coverity complains that "bt" may > > be a NULL pointer here, since we checked it for NULL above. > > > > CID 1460458: Null pointer dereferences (FORWARD_NULL) > > > >> else if (attr == &dev_attr_pid) > >> - q->blk_trace->pid = value; > >> + bt->pid = value; > >> else if (attr == &dev_attr_start_lba) > >> - q->blk_trace->start_lba = value; > >> + bt->start_lba = value; > >> else if (attr == &dev_attr_end_lba) > >> - q->blk_trace->end_lba = value; > >> + bt->end_lba = value; > >> } > >> > >> out_unlock_bdev: > >> > > >
On Mon, Mar 02, 2020 at 09:19:33PM +0000, Chaitanya Kulkarni wrote: > By any chance will the following patch be able to get rid of > the warning ? > > index 4560878f0bac..889555910555 100644 > --- a/kernel/trace/blktrace.c > +++ b/kernel/trace/blktrace.c > @@ -1895,9 +1895,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct > device *dev, > goto out_unlock_bdev; > } > > - ret = 0; > - if (bt == NULL) > - ret = blk_trace_setup_queue(q, bdev); > + ret = bt == NULL ? blk_trace_setup_queue(q, bdev) : 0; > > if (ret == 0) { > if (attr == &dev_attr_act_mask) That looks the same thing as what created the warning, just more compact. I think the right thing to do is update bt to the one allocated from a successful blk_trace_setup_queue().
Added a reassignment into the NULL check block to fix the issue.
Fixes: c780e86dd48 ("blktrace: Protect q->blk_trace with RCU")
Signed-off-by: Cengiz Can <cengiz@kernel.wtf>
---
kernel/trace/blktrace.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 4560878f0bac..29ea88f10b87 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -1896,8 +1896,10 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
}
ret = 0;
- if (bt == NULL)
+ if (bt == NULL) {
ret = blk_trace_setup_queue(q, bdev);
+ bt = q->blk_trace;
+ }
if (ret == 0) {
if (attr == &dev_attr_act_mask)
--
2.25.1
On Tue, Mar 03, 2020 at 02:07:32PM +0300, Cengiz Can wrote: > Added a reassignment into the NULL check block to fix the issue. > > Fixes: c780e86dd48 ("blktrace: Protect q->blk_trace with RCU") > > Signed-off-by: Cengiz Can <cengiz@kernel.wtf> > --- > kernel/trace/blktrace.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c > index 4560878f0bac..29ea88f10b87 100644 > --- a/kernel/trace/blktrace.c > +++ b/kernel/trace/blktrace.c > @@ -1896,8 +1896,10 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, > } > > ret = 0; > - if (bt == NULL) > + if (bt == NULL) { > ret = blk_trace_setup_queue(q, bdev); > + bt = q->blk_trace; > + } > > if (ret == 0) { > if (attr == &dev_attr_act_mask) > -- > 2.25.1 > <formletter> This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly. </formletter>
On Tue, Mar 3, 2020 at 8:37 PM Cengiz Can <cengiz@kernel.wtf> wrote: > > Added a reassignment into the NULL check block to fix the issue. > > Fixes: c780e86dd48 ("blktrace: Protect q->blk_trace with RCU") > > Signed-off-by: Cengiz Can <cengiz@kernel.wtf> > --- > kernel/trace/blktrace.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c > index 4560878f0bac..29ea88f10b87 100644 > --- a/kernel/trace/blktrace.c > +++ b/kernel/trace/blktrace.c > @@ -1896,8 +1896,10 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, > } > > ret = 0; > - if (bt == NULL) > + if (bt == NULL) { > ret = blk_trace_setup_queue(q, bdev); > + bt = q->blk_trace; I'd suggest to use the following line for avoiding RCU warning: bt = rcu_dereference_protected(q->blk_trace, lockdep_is_held(&q->blk_trace_mutex)); Otherwise, the patch looks fine for me: Reviewed-by: Ming Lei <ming.lei@redhat.com> Thanks, Ming Lei
On March 5, 2020 04:51:51 Ming Lei <tom.leiming@gmail.com> wrote: > On Tue, Mar 3, 2020 at 8:37 PM Cengiz Can <cengiz@kernel.wtf> wrote: >> >> Added a reassignment into the NULL check block to fix the issue. >> >> Fixes: c780e86dd48 ("blktrace: Protect q->blk_trace with RCU") >> >> Signed-off-by: Cengiz Can <cengiz@kernel.wtf> >> --- >> kernel/trace/blktrace.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c >> index 4560878f0bac..29ea88f10b87 100644 >> --- a/kernel/trace/blktrace.c >> +++ b/kernel/trace/blktrace.c >> @@ -1896,8 +1896,10 @@ static ssize_t sysfs_blk_trace_attr_store(struct >> device *dev, >> } >> >> ret = 0; >> - if (bt == NULL) >> + if (bt == NULL) { >> ret = blk_trace_setup_queue(q, bdev); >> + bt = q->blk_trace; > > I'd suggest to use the following line for avoiding RCU warning: > > bt = rcu_dereference_protected(q->blk_trace, > lockdep_is_held(&q->blk_trace_mutex)); > > Otherwise, the patch looks fine for me: Thank you. Please kindly see v2. > > Reviewed-by: Ming Lei <ming.lei@redhat.com> > > Thanks, > Ming Lei
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 4c636c42ad68..1cb5afed5515 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -524,7 +524,7 @@ struct request_queue { unsigned int sg_reserved_size; int node; #ifdef CONFIG_BLK_DEV_IO_TRACE - struct blk_trace *blk_trace; + struct blk_trace __rcu *blk_trace; struct mutex blk_trace_mutex; #endif /* diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h index 7bb2d8de9f30..3b6ff5902edc 100644 --- a/include/linux/blktrace_api.h +++ b/include/linux/blktrace_api.h @@ -51,9 +51,13 @@ void __trace_note_message(struct blk_trace *, struct blkcg *blkcg, const char *f **/ #define blk_add_cgroup_trace_msg(q, cg, fmt, ...) \ do { \ - struct blk_trace *bt = (q)->blk_trace; \ + struct blk_trace *bt; \ + \ + rcu_read_lock(); \ + bt = rcu_dereference((q)->blk_trace); \ if (unlikely(bt)) \ __trace_note_message(bt, cg, fmt, ##__VA_ARGS__);\ + rcu_read_unlock(); \ } while (0) #define blk_add_trace_msg(q, fmt, ...) \ blk_add_cgroup_trace_msg(q, NULL, fmt, ##__VA_ARGS__) @@ -61,10 +65,14 @@ void __trace_note_message(struct blk_trace *, struct blkcg *blkcg, const char *f static inline bool blk_trace_note_message_enabled(struct request_queue *q) { - struct blk_trace *bt = q->blk_trace; - if (likely(!bt)) - return false; - return bt->act_mask & BLK_TC_NOTIFY; + struct blk_trace *bt; + bool ret; + + rcu_read_lock(); + bt = rcu_dereference(q->blk_trace); + ret = bt && (bt->act_mask & BLK_TC_NOTIFY); + rcu_read_unlock(); + return ret; } extern void blk_add_driver_data(struct request_queue *q, struct request *rq, diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index 475e29498bca..a6d3016410eb 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -335,6 +335,7 @@ static void put_probe_ref(void) static void blk_trace_cleanup(struct blk_trace *bt) { + synchronize_rcu(); blk_trace_free(bt); put_probe_ref(); } @@ -629,8 +630,10 @@ static int compat_blk_trace_setup(struct request_queue *q, char *name, static int __blk_trace_startstop(struct request_queue *q, int start) { int ret; - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; + bt = rcu_dereference_protected(q->blk_trace, + lockdep_is_held(&q->blk_trace_mutex)); if (bt == NULL) return -EINVAL; @@ -740,8 +743,8 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg) void blk_trace_shutdown(struct request_queue *q) { mutex_lock(&q->blk_trace_mutex); - - if (q->blk_trace) { + if (rcu_dereference_protected(q->blk_trace, + lockdep_is_held(&q->blk_trace_mutex))) { __blk_trace_startstop(q, 0); __blk_trace_remove(q); } @@ -752,8 +755,10 @@ void blk_trace_shutdown(struct request_queue *q) #ifdef CONFIG_BLK_CGROUP static u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio) { - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; + /* We don't use the 'bt' value here except as an optimization... */ + bt = rcu_dereference_protected(q->blk_trace, 1); if (!bt || !(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP)) return 0; @@ -796,10 +801,14 @@ blk_trace_request_get_cgid(struct request_queue *q, struct request *rq) static void blk_add_trace_rq(struct request *rq, int error, unsigned int nr_bytes, u32 what, u64 cgid) { - struct blk_trace *bt = rq->q->blk_trace; + struct blk_trace *bt; - if (likely(!bt)) + rcu_read_lock(); + bt = rcu_dereference(rq->q->blk_trace); + if (likely(!bt)) { + rcu_read_unlock(); return; + } if (blk_rq_is_passthrough(rq)) what |= BLK_TC_ACT(BLK_TC_PC); @@ -808,6 +817,7 @@ static void blk_add_trace_rq(struct request *rq, int error, __blk_add_trace(bt, blk_rq_trace_sector(rq), nr_bytes, req_op(rq), rq->cmd_flags, what, error, 0, NULL, cgid); + rcu_read_unlock(); } static void blk_add_trace_rq_insert(void *ignore, @@ -853,14 +863,19 @@ static void blk_add_trace_rq_complete(void *ignore, struct request *rq, static void blk_add_trace_bio(struct request_queue *q, struct bio *bio, u32 what, int error) { - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; - if (likely(!bt)) + rcu_read_lock(); + bt = rcu_dereference(q->blk_trace); + if (likely(!bt)) { + rcu_read_unlock(); return; + } __blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size, bio_op(bio), bio->bi_opf, what, error, 0, NULL, blk_trace_bio_get_cgid(q, bio)); + rcu_read_unlock(); } static void blk_add_trace_bio_bounce(void *ignore, @@ -905,11 +920,14 @@ static void blk_add_trace_getrq(void *ignore, if (bio) blk_add_trace_bio(q, bio, BLK_TA_GETRQ, 0); else { - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; + rcu_read_lock(); + bt = rcu_dereference(q->blk_trace); if (bt) __blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_GETRQ, 0, 0, NULL, 0); + rcu_read_unlock(); } } @@ -921,27 +939,35 @@ static void blk_add_trace_sleeprq(void *ignore, if (bio) blk_add_trace_bio(q, bio, BLK_TA_SLEEPRQ, 0); else { - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; + rcu_read_lock(); + bt = rcu_dereference(q->blk_trace); if (bt) __blk_add_trace(bt, 0, 0, rw, 0, BLK_TA_SLEEPRQ, 0, 0, NULL, 0); + rcu_read_unlock(); } } static void blk_add_trace_plug(void *ignore, struct request_queue *q) { - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; + rcu_read_lock(); + bt = rcu_dereference(q->blk_trace); if (bt) __blk_add_trace(bt, 0, 0, 0, 0, BLK_TA_PLUG, 0, 0, NULL, 0); + rcu_read_unlock(); } static void blk_add_trace_unplug(void *ignore, struct request_queue *q, unsigned int depth, bool explicit) { - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; + rcu_read_lock(); + bt = rcu_dereference(q->blk_trace); if (bt) { __be64 rpdu = cpu_to_be64(depth); u32 what; @@ -953,14 +979,17 @@ static void blk_add_trace_unplug(void *ignore, struct request_queue *q, __blk_add_trace(bt, 0, 0, 0, 0, what, 0, sizeof(rpdu), &rpdu, 0); } + rcu_read_unlock(); } static void blk_add_trace_split(void *ignore, struct request_queue *q, struct bio *bio, unsigned int pdu) { - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; + rcu_read_lock(); + bt = rcu_dereference(q->blk_trace); if (bt) { __be64 rpdu = cpu_to_be64(pdu); @@ -969,6 +998,7 @@ static void blk_add_trace_split(void *ignore, BLK_TA_SPLIT, bio->bi_status, sizeof(rpdu), &rpdu, blk_trace_bio_get_cgid(q, bio)); } + rcu_read_unlock(); } /** @@ -988,11 +1018,15 @@ static void blk_add_trace_bio_remap(void *ignore, struct request_queue *q, struct bio *bio, dev_t dev, sector_t from) { - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; struct blk_io_trace_remap r; - if (likely(!bt)) + rcu_read_lock(); + bt = rcu_dereference(q->blk_trace); + if (likely(!bt)) { + rcu_read_unlock(); return; + } r.device_from = cpu_to_be32(dev); r.device_to = cpu_to_be32(bio_dev(bio)); @@ -1001,6 +1035,7 @@ static void blk_add_trace_bio_remap(void *ignore, __blk_add_trace(bt, bio->bi_iter.bi_sector, bio->bi_iter.bi_size, bio_op(bio), bio->bi_opf, BLK_TA_REMAP, bio->bi_status, sizeof(r), &r, blk_trace_bio_get_cgid(q, bio)); + rcu_read_unlock(); } /** @@ -1021,11 +1056,15 @@ static void blk_add_trace_rq_remap(void *ignore, struct request *rq, dev_t dev, sector_t from) { - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; struct blk_io_trace_remap r; - if (likely(!bt)) + rcu_read_lock(); + bt = rcu_dereference(q->blk_trace); + if (likely(!bt)) { + rcu_read_unlock(); return; + } r.device_from = cpu_to_be32(dev); r.device_to = cpu_to_be32(disk_devt(rq->rq_disk)); @@ -1034,6 +1073,7 @@ static void blk_add_trace_rq_remap(void *ignore, __blk_add_trace(bt, blk_rq_pos(rq), blk_rq_bytes(rq), rq_data_dir(rq), 0, BLK_TA_REMAP, 0, sizeof(r), &r, blk_trace_request_get_cgid(q, rq)); + rcu_read_unlock(); } /** @@ -1051,14 +1091,19 @@ void blk_add_driver_data(struct request_queue *q, struct request *rq, void *data, size_t len) { - struct blk_trace *bt = q->blk_trace; + struct blk_trace *bt; - if (likely(!bt)) + rcu_read_lock(); + bt = rcu_dereference(q->blk_trace); + if (likely(!bt)) { + rcu_read_unlock(); return; + } __blk_add_trace(bt, blk_rq_trace_sector(rq), blk_rq_bytes(rq), 0, 0, BLK_TA_DRV_DATA, 0, len, data, blk_trace_request_get_cgid(q, rq)); + rcu_read_unlock(); } EXPORT_SYMBOL_GPL(blk_add_driver_data); @@ -1597,6 +1642,7 @@ static int blk_trace_remove_queue(struct request_queue *q) return -EINVAL; put_probe_ref(); + synchronize_rcu(); blk_trace_free(bt); return 0; } @@ -1758,6 +1804,7 @@ static ssize_t sysfs_blk_trace_attr_show(struct device *dev, struct hd_struct *p = dev_to_part(dev); struct request_queue *q; struct block_device *bdev; + struct blk_trace *bt; ssize_t ret = -ENXIO; bdev = bdget(part_devt(p)); @@ -1770,21 +1817,23 @@ static ssize_t sysfs_blk_trace_attr_show(struct device *dev, mutex_lock(&q->blk_trace_mutex); + bt = rcu_dereference_protected(q->blk_trace, + lockdep_is_held(&q->blk_trace_mutex)); if (attr == &dev_attr_enable) { - ret = sprintf(buf, "%u\n", !!q->blk_trace); + ret = sprintf(buf, "%u\n", !!bt); goto out_unlock_bdev; } - if (q->blk_trace == NULL) + if (bt == NULL) ret = sprintf(buf, "disabled\n"); else if (attr == &dev_attr_act_mask) - ret = blk_trace_mask2str(buf, q->blk_trace->act_mask); + ret = blk_trace_mask2str(buf, bt->act_mask); else if (attr == &dev_attr_pid) - ret = sprintf(buf, "%u\n", q->blk_trace->pid); + ret = sprintf(buf, "%u\n", bt->pid); else if (attr == &dev_attr_start_lba) - ret = sprintf(buf, "%llu\n", q->blk_trace->start_lba); + ret = sprintf(buf, "%llu\n", bt->start_lba); else if (attr == &dev_attr_end_lba) - ret = sprintf(buf, "%llu\n", q->blk_trace->end_lba); + ret = sprintf(buf, "%llu\n", bt->end_lba); out_unlock_bdev: mutex_unlock(&q->blk_trace_mutex); @@ -1801,6 +1850,7 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, struct block_device *bdev; struct request_queue *q; struct hd_struct *p; + struct blk_trace *bt; u64 value; ssize_t ret = -EINVAL; @@ -1831,8 +1881,10 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, mutex_lock(&q->blk_trace_mutex); + bt = rcu_dereference_protected(q->blk_trace, + lockdep_is_held(&q->blk_trace_mutex)); if (attr == &dev_attr_enable) { - if (!!value == !!q->blk_trace) { + if (!!value == !!bt) { ret = 0; goto out_unlock_bdev; } @@ -1844,18 +1896,18 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev, } ret = 0; - if (q->blk_trace == NULL) + if (bt == NULL) ret = blk_trace_setup_queue(q, bdev); if (ret == 0) { if (attr == &dev_attr_act_mask) - q->blk_trace->act_mask = value; + bt->act_mask = value; else if (attr == &dev_attr_pid) - q->blk_trace->pid = value; + bt->pid = value; else if (attr == &dev_attr_start_lba) - q->blk_trace->start_lba = value; + bt->start_lba = value; else if (attr == &dev_attr_end_lba) - q->blk_trace->end_lba = value; + bt->end_lba = value; } out_unlock_bdev:
KASAN is reporting that __blk_add_trace() has a use-after-free issue when accessing q->blk_trace. Indeed the switching of block tracing (and thus eventual freeing of q->blk_trace) is completely unsynchronized with the currently running tracing and thus it can happen that the blk_trace structure is being freed just while __blk_add_trace() works on it. Protect accesses to q->blk_trace by RCU during tracing and make sure we wait for the end of RCU grace period when shutting down tracing. Luckily that is rare enough event that we can afford that. Note that postponing the freeing of blk_trace to an RCU callback should better be avoided as it could have unexpected user visible side-effects as debugfs files would be still existing for a short while block tracing has been shut down. Link: https://bugzilla.kernel.org/show_bug.cgi?id=205711 CC: stable@vger.kernel.org Reported-by: Tristan <tristmd@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz> --- include/linux/blkdev.h | 2 +- include/linux/blktrace_api.h | 18 +++++-- kernel/trace/blktrace.c | 114 +++++++++++++++++++++++++++++++------------ 3 files changed, 97 insertions(+), 37 deletions(-)