@@ -85,6 +85,7 @@
static DEFINE_IDR(loop_index_idr);
static DEFINE_MUTEX(loop_index_mutex);
+static DEFINE_MUTEX(loop_ctl_mutex);
static int max_part;
static int part_shift;
@@ -1048,7 +1049,7 @@ static int loop_clr_fd(struct loop_device *lo)
*/
if (atomic_read(&lo->lo_refcnt) > 1) {
lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
return 0;
}
@@ -1101,12 +1102,12 @@ static int loop_clr_fd(struct loop_device *lo)
if (!part_shift)
lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
loop_unprepare_queue(lo);
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
/*
- * Need not hold lo_ctl_mutex to fput backing file.
- * Calling fput holding lo_ctl_mutex triggers a circular
+ * Need not hold loop_ctl_mutex to fput backing file.
+ * Calling fput holding loop_ctl_mutex triggers a circular
* lock dependency possibility warning as fput can take
- * bd_mutex which is usually taken before lo_ctl_mutex.
+ * bd_mutex which is usually taken before loop_ctl_mutex.
*/
fput(filp);
return 0;
@@ -1211,7 +1212,7 @@ static int loop_clr_fd(struct loop_device *lo)
int ret;
if (lo->lo_state != Lo_bound) {
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
return -ENXIO;
}
@@ -1230,10 +1231,10 @@ static int loop_clr_fd(struct loop_device *lo)
lo->lo_encrypt_key_size);
}
- /* Drop lo_ctl_mutex while we call into the filesystem. */
+ /* Drop loop_ctl_mutex while we call into the filesystem. */
path = lo->lo_backing_file->f_path;
path_get(&path);
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
ret = vfs_getattr(&path, &stat, STATX_INO, AT_STATX_SYNC_AS_STAT);
if (!ret) {
info->lo_device = huge_encode_dev(stat.dev);
@@ -1325,7 +1326,7 @@ static int loop_clr_fd(struct loop_device *lo)
int err;
if (!arg) {
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
return -EINVAL;
}
err = loop_get_status(lo, &info64);
@@ -1343,7 +1344,7 @@ static int loop_clr_fd(struct loop_device *lo)
int err;
if (!arg) {
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
return -EINVAL;
}
err = loop_get_status(lo, &info64);
@@ -1401,7 +1402,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
struct loop_device *lo = bdev->bd_disk->private_data;
int err;
- err = mutex_lock_killable_nested(&lo->lo_ctl_mutex, 1);
+ err = mutex_lock_killable_nested(&loop_ctl_mutex, 1);
if (err)
goto out_unlocked;
@@ -1413,7 +1414,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
err = loop_change_fd(lo, bdev, arg);
break;
case LOOP_CLR_FD:
- /* loop_clr_fd would have unlocked lo_ctl_mutex on success */
+ /* loop_clr_fd would have unlocked loop_ctl_mutex on success */
err = loop_clr_fd(lo);
if (!err)
goto out_unlocked;
@@ -1426,7 +1427,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
break;
case LOOP_GET_STATUS:
err = loop_get_status_old(lo, (struct loop_info __user *) arg);
- /* loop_get_status() unlocks lo_ctl_mutex */
+ /* loop_get_status() unlocks loop_ctl_mutex */
goto out_unlocked;
case LOOP_SET_STATUS64:
err = -EPERM;
@@ -1436,7 +1437,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
break;
case LOOP_GET_STATUS64:
err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
- /* loop_get_status() unlocks lo_ctl_mutex */
+ /* loop_get_status() unlocks loop_ctl_mutex */
goto out_unlocked;
case LOOP_SET_CAPACITY:
err = -EPERM;
@@ -1456,7 +1457,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
default:
err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
}
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
out_unlocked:
return err;
@@ -1573,7 +1574,7 @@ struct compat_loop_info {
int err;
if (!arg) {
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
return -EINVAL;
}
err = loop_get_status(lo, &info64);
@@ -1590,19 +1591,19 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
switch(cmd) {
case LOOP_SET_STATUS:
- err = mutex_lock_killable(&lo->lo_ctl_mutex);
+ err = mutex_lock_killable(&loop_ctl_mutex);
if (!err) {
err = loop_set_status_compat(lo,
(const struct compat_loop_info __user *)arg);
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
}
break;
case LOOP_GET_STATUS:
- err = mutex_lock_killable(&lo->lo_ctl_mutex);
+ err = mutex_lock_killable(&loop_ctl_mutex);
if (!err) {
err = loop_get_status_compat(lo,
(struct compat_loop_info __user *)arg);
- /* loop_get_status() unlocks lo_ctl_mutex */
+ /* loop_get_status() unlocks loop_ctl_mutex */
}
break;
case LOOP_SET_CAPACITY:
@@ -1649,7 +1650,7 @@ static void __lo_release(struct loop_device *lo)
if (atomic_dec_return(&lo->lo_refcnt))
return;
- mutex_lock(&lo->lo_ctl_mutex);
+ mutex_lock(&loop_ctl_mutex);
if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
/*
* In autoclear mode, stop the loop thread
@@ -1667,7 +1668,7 @@ static void __lo_release(struct loop_device *lo)
blk_mq_unfreeze_queue(lo->lo_queue);
}
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
}
static void lo_release(struct gendisk *disk, fmode_t mode)
@@ -1713,10 +1714,10 @@ static int unregister_transfer_cb(int id, void *ptr, void *data)
struct loop_device *lo = ptr;
struct loop_func_table *xfer = data;
- mutex_lock(&lo->lo_ctl_mutex);
+ mutex_lock(&loop_ctl_mutex);
if (lo->lo_encryption == xfer)
loop_release_xfer(lo);
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
return 0;
}
@@ -1897,7 +1898,7 @@ static int loop_add(struct loop_device **l, int i)
if (!part_shift)
disk->flags |= GENHD_FL_NO_PART_SCAN;
disk->flags |= GENHD_FL_EXT_DEVT;
- mutex_init(&lo->lo_ctl_mutex);
+ mutex_init(&loop_ctl_mutex);
atomic_set(&lo->lo_refcnt, 0);
lo->lo_number = i;
spin_lock_init(&lo->lo_lock);
@@ -2010,21 +2011,21 @@ static long loop_control_ioctl(struct file *file, unsigned int cmd,
ret = loop_lookup(&lo, parm);
if (ret < 0)
break;
- ret = mutex_lock_killable(&lo->lo_ctl_mutex);
+ ret = mutex_lock_killable(&loop_ctl_mutex);
if (ret)
break;
if (lo->lo_state != Lo_unbound) {
ret = -EBUSY;
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
break;
}
if (atomic_read(&lo->lo_refcnt) > 0) {
ret = -EBUSY;
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
break;
}
lo->lo_disk->private_data = NULL;
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
idr_remove(&loop_index_idr, lo->lo_number);
loop_remove(lo);
break;
@@ -54,7 +54,6 @@ struct loop_device {
spinlock_t lo_lock;
int lo_state;
- struct mutex lo_ctl_mutex;
struct kthread_worker worker;
struct task_struct *worker_task;
bool use_dio;
syzbot is reporting NULL pointer dereference [1] which is caused by race condition between ioctl(loop_fd, LOOP_CLR_FD, 0) versus ioctl(other_loop_fd, LOOP_SET_FD, loop_fd) due to traversing other loop devices at loop_validate_file() without holding corresponding lo->lo_ctl_mutex locks. Since ioctl() request on loop devices is not frequent operation, we don't need fine grained locking. Let's use global lock in order to allow safe traversal at loop_validate_file(). Note that syzbot is also reporting circular locking dependency between bdev->bd_mutex and lo->lo_ctl_mutex [2] which is caused by calling blkdev_reread_part() with lock held. This patch does not address it. [1] https://syzkaller.appspot.com/bug?id=f3cfe26e785d85f9ee259f385515291d21bd80a3 [2] https://syzkaller.appspot.com/bug?id=bf154052f0eea4bc7712499e4569505907d15889 Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reported-by: syzbot <syzbot+bf89c128e05dd6c62523@syzkaller.appspotmail.com> --- drivers/block/loop.c | 59 ++++++++++++++++++++++++++-------------------------- drivers/block/loop.h | 1 - 2 files changed, 30 insertions(+), 30 deletions(-)