| Message ID | 20210318171111.706303-10-samitolvanen@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add support for Clang CFI | expand |
On Thu, Mar 18, 2021 at 10:11 AM Sami Tolvanen <samitolvanen@google.com> wrote: > > Casting the comparison function to a different type trips indirect > call Control-Flow Integrity (CFI) checking. Remove the additional > consts from cmp_func, and the now unneeded casts. > > Fixes: 043b3f7b6388 ("lib/list_sort: simplify and remove MAX_LIST_LENGTH_BITS") > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > Reviewed-by: Kees Cook <keescook@chromium.org> > --- > lib/list_sort.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/lib/list_sort.c b/lib/list_sort.c > index 52f0c258c895..b14accf4ef83 100644 > --- a/lib/list_sort.c > +++ b/lib/list_sort.c > @@ -8,7 +8,7 @@ > #include <linux/list.h> > > typedef int __attribute__((nonnull(2,3))) (*cmp_func)(void *, > - struct list_head const *, struct list_head const *); > + struct list_head *, struct list_head *); > > /* > * Returns a list organized in an intermediate format suited > @@ -227,7 +227,7 @@ void list_sort(void *priv, struct list_head *head, There's definitely some const confusion going on around here. Comparison functions that modify their in/out parameters are a code smell, and I wonder if any exist in tree? I think it would be better to enforce one signature for cmp_func throughout lib/list_sort.c and the tree, either const or not, but not a mix of both. I know `const` is messy because it tends to propagate everywhere, so I don't care which is preferred (making cmp_func have const qualified params or not, though if we're already being pedantic about which params are non-null...), but something like this might be nicer: ``` diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 5132f64a5cee..d475b3cfd06f 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -75,7 +75,8 @@ void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx) blk_mq_run_hw_queue(hctx, true); } -static int sched_rq_cmp(void *priv, struct list_head *a, struct list_head *b) +static int sched_rq_cmp(void *priv, const struct list_head *a, + const struct list_head *b) { struct request *rqa = container_of(a, struct request, queuelist); struct request *rqb = container_of(b, struct request, queuelist); diff --git a/block/blk-mq.c b/block/blk-mq.c index 2e825a7a3606..9ed063ffdb27 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1905,7 +1905,8 @@ void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, spin_unlock(&ctx->lock); } -static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b) +static int plug_rq_cmp(void *priv, const struct list_head *a, + const struct list_head *b) { struct request *rqa = container_of(a, struct request, queuelist); struct request *rqb = container_of(b, struct request, queuelist); diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c index 1ac67d4505e0..5a3a343499f6 100644 --- a/drivers/gpu/drm/drm_modes.c +++ b/drivers/gpu/drm/drm_modes.c @@ -1290,7 +1290,8 @@ EXPORT_SYMBOL(drm_mode_prune_invalid); * Negative if @lh_a is better than @lh_b, zero if they're equivalent, or * positive if @lh_b is better than @lh_a. */ -static int drm_mode_compare(void *priv, struct list_head *lh_a, struct list_head *lh_b) +static int drm_mode_compare(void *priv, const struct list_head *lh_a, + const struct list_head *lh_b) { struct drm_display_mode *a = list_entry(lh_a, struct drm_display_mode, head); struct drm_display_mode *b = list_entry(lh_b, struct drm_display_mode, head); diff --git a/drivers/gpu/drm/i915/gt/intel_engine_user.c b/drivers/gpu/drm/i915/gt/intel_engine_user.c index 34e6096f196e..7586dffd27d3 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_user.c +++ b/drivers/gpu/drm/i915/gt/intel_engine_user.c @@ -49,7 +49,8 @@ static const u8 uabi_classes[] = { [VIDEO_ENHANCEMENT_CLASS] = I915_ENGINE_CLASS_VIDEO_ENHANCE, }; -static int engine_cmp(void *priv, struct list_head *A, struct list_head *B) +static int engine_cmp(void *priv, const struct list_head *A, + const struct list_head *B) { const struct intel_engine_cs *a = container_of((struct rb_node *)A, typeof(*a), uabi_node); diff --git a/fs/ext4/fsmap.c b/fs/ext4/fsmap.c index 4c2a9fe30067..4493ef0c715e 100644 --- a/fs/ext4/fsmap.c +++ b/fs/ext4/fsmap.c @@ -354,8 +354,8 @@ static unsigned int ext4_getfsmap_find_sb(struct super_block *sb, /* Compare two fsmap items. */ static int ext4_getfsmap_compare(void *priv, - struct list_head *a, - struct list_head *b) + const struct list_head *a, + const struct list_head *b) { struct ext4_fsmap *fa; struct ext4_fsmap *fb; diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index 414769a6ad11..0129e6bab985 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -1155,7 +1155,8 @@ iomap_ioend_try_merge(struct iomap_ioend *ioend, struct list_head *more_ioends, EXPORT_SYMBOL_GPL(iomap_ioend_try_merge); static int -iomap_ioend_compare(void *priv, struct list_head *a, struct list_head *b) +iomap_ioend_compare(void *priv, const struct list_head *a, + const struct list_head *b) { struct iomap_ioend *ia = container_of(a, struct iomap_ioend, io_list); struct iomap_ioend *ib = container_of(b, struct iomap_ioend, io_list); diff --git a/include/linux/list_sort.h b/include/linux/list_sort.h index 20f178c24e9d..4fe9cb94d0d1 100644 --- a/include/linux/list_sort.h +++ b/include/linux/list_sort.h @@ -6,8 +6,9 @@ struct list_head; +typedef int __attribute__((nonnull(2,3))) (*cmp_func)(void *, + struct list_head const *, struct list_head const *); + __attribute__((nonnull(2,3))) -void list_sort(void *priv, struct list_head *head, - int (*cmp)(void *priv, struct list_head *a, - struct list_head *b)); +void list_sort(void *priv, struct list_head *head, cmp_func cmp); #endif diff --git a/lib/list_sort.c b/lib/list_sort.c index 52f0c258c895..6cfac649c4a6 100644 --- a/lib/list_sort.c +++ b/lib/list_sort.c @@ -7,9 +7,6 @@ #include <linux/list_sort.h> #include <linux/list.h> -typedef int __attribute__((nonnull(2,3))) (*cmp_func)(void *, - struct list_head const *, struct list_head const *); - /* * Returns a list organized in an intermediate format suited * to chaining of merge() calls: null-terminated, no reserved or @@ -185,9 +182,7 @@ static void merge_final(void *priv, cmp_func cmp, struct list_head *head, * 2^(k+1) - 1 (second merge of case 5 when x == 2^(k-1) - 1). */ __attribute__((nonnull(2,3))) -void list_sort(void *priv, struct list_head *head, - int (*cmp)(void *priv, struct list_head *a, - struct list_head *b)) +void list_sort(void *priv, struct list_head *head, cmp_func cmp) { struct list_head *list = head->next, *pending = NULL; size_t count = 0; /* Count of pending */ ``` There are probably more instances in the tree to clean up, but that compiles with x86_64 defconfig, and I'm sure it doesn't suffer the CFI issue from the cast. > if (likely(bits)) { > struct list_head *a = *tail, *b = a->prev; > > - a = merge(priv, (cmp_func)cmp, b, a); > + a = merge(priv, cmp, b, a); > /* Install the merged result in place of the inputs */ > a->prev = b->prev; > *tail = a; > @@ -249,10 +249,10 @@ void list_sort(void *priv, struct list_head *head, > > if (!next) > break; > - list = merge(priv, (cmp_func)cmp, pending, list); > + list = merge(priv, cmp, pending, list); > pending = next; > } > /* The final merge, rebuilding prev links */ > - merge_final(priv, (cmp_func)cmp, head, pending, list); > + merge_final(priv, cmp, head, pending, list); > } > EXPORT_SYMBOL(list_sort); > -- > 2.31.0.291.g576ba9dcdaf-goog >
On Thu, Mar 18, 2021 at 11:31 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Thu, Mar 18, 2021 at 10:11 AM Sami Tolvanen <samitolvanen@google.com> wrote: > > > > Casting the comparison function to a different type trips indirect > > call Control-Flow Integrity (CFI) checking. Remove the additional > > consts from cmp_func, and the now unneeded casts. > > > > Fixes: 043b3f7b6388 ("lib/list_sort: simplify and remove MAX_LIST_LENGTH_BITS") > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > Reviewed-by: Kees Cook <keescook@chromium.org> > > --- > > lib/list_sort.c | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/lib/list_sort.c b/lib/list_sort.c > > index 52f0c258c895..b14accf4ef83 100644 > > --- a/lib/list_sort.c > > +++ b/lib/list_sort.c > > @@ -8,7 +8,7 @@ > > #include <linux/list.h> > > > > typedef int __attribute__((nonnull(2,3))) (*cmp_func)(void *, > > - struct list_head const *, struct list_head const *); > > + struct list_head *, struct list_head *); > > > > /* > > * Returns a list organized in an intermediate format suited > > @@ -227,7 +227,7 @@ void list_sort(void *priv, struct list_head *head, > > There's definitely some const confusion going on around here. > Comparison functions that modify their in/out parameters are a code > smell, and I wonder if any exist in tree? > > I think it would be better to enforce one signature for cmp_func > throughout lib/list_sort.c and the tree, either const or not, but not > a mix of both. I know `const` is messy because it tends to propagate > everywhere, so I don't care which is preferred (making cmp_func have > const qualified params or not, though if we're already being pedantic > about which params are non-null...), but something like this might be > nicer: Sure, an alternative to removing the internal casts is to actually change all the callers to use a comparison function with const parameters. That's quite a bit more invasive, but I'm fine with that approach too. > > ``` > diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c > index 5132f64a5cee..d475b3cfd06f 100644 > --- a/block/blk-mq-sched.c > +++ b/block/blk-mq-sched.c > @@ -75,7 +75,8 @@ void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx) > blk_mq_run_hw_queue(hctx, true); > } > > -static int sched_rq_cmp(void *priv, struct list_head *a, struct list_head *b) > +static int sched_rq_cmp(void *priv, const struct list_head *a, > + const struct list_head *b) > { > struct request *rqa = container_of(a, struct request, queuelist); > struct request *rqb = container_of(b, struct request, queuelist); > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 2e825a7a3606..9ed063ffdb27 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -1905,7 +1905,8 @@ void blk_mq_insert_requests(struct blk_mq_hw_ctx > *hctx, struct blk_mq_ctx *ctx, > spin_unlock(&ctx->lock); > } > > -static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b) > +static int plug_rq_cmp(void *priv, const struct list_head *a, > + const struct list_head *b) > { > struct request *rqa = container_of(a, struct request, queuelist); > struct request *rqb = container_of(b, struct request, queuelist); > diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c > index 1ac67d4505e0..5a3a343499f6 100644 > --- a/drivers/gpu/drm/drm_modes.c > +++ b/drivers/gpu/drm/drm_modes.c > @@ -1290,7 +1290,8 @@ EXPORT_SYMBOL(drm_mode_prune_invalid); > * Negative if @lh_a is better than @lh_b, zero if they're equivalent, or > * positive if @lh_b is better than @lh_a. > */ > -static int drm_mode_compare(void *priv, struct list_head *lh_a, > struct list_head *lh_b) > +static int drm_mode_compare(void *priv, const struct list_head *lh_a, > + const struct list_head *lh_b) > { > struct drm_display_mode *a = list_entry(lh_a, struct > drm_display_mode, head); > struct drm_display_mode *b = list_entry(lh_b, struct > drm_display_mode, head); > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_user.c > b/drivers/gpu/drm/i915/gt/intel_engine_user.c > index 34e6096f196e..7586dffd27d3 100644 > --- a/drivers/gpu/drm/i915/gt/intel_engine_user.c > +++ b/drivers/gpu/drm/i915/gt/intel_engine_user.c > @@ -49,7 +49,8 @@ static const u8 uabi_classes[] = { > [VIDEO_ENHANCEMENT_CLASS] = I915_ENGINE_CLASS_VIDEO_ENHANCE, > }; > > -static int engine_cmp(void *priv, struct list_head *A, struct list_head *B) > +static int engine_cmp(void *priv, const struct list_head *A, > + const struct list_head *B) > { > const struct intel_engine_cs *a = > container_of((struct rb_node *)A, typeof(*a), uabi_node); > diff --git a/fs/ext4/fsmap.c b/fs/ext4/fsmap.c > index 4c2a9fe30067..4493ef0c715e 100644 > --- a/fs/ext4/fsmap.c > +++ b/fs/ext4/fsmap.c > @@ -354,8 +354,8 @@ static unsigned int ext4_getfsmap_find_sb(struct > super_block *sb, > > /* Compare two fsmap items. */ > static int ext4_getfsmap_compare(void *priv, > - struct list_head *a, > - struct list_head *b) > + const struct list_head *a, > + const struct list_head *b) > { > struct ext4_fsmap *fa; > struct ext4_fsmap *fb; > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index 414769a6ad11..0129e6bab985 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -1155,7 +1155,8 @@ iomap_ioend_try_merge(struct iomap_ioend *ioend, > struct list_head *more_ioends, > EXPORT_SYMBOL_GPL(iomap_ioend_try_merge); > > static int > -iomap_ioend_compare(void *priv, struct list_head *a, struct list_head *b) > +iomap_ioend_compare(void *priv, const struct list_head *a, > + const struct list_head *b) > { > struct iomap_ioend *ia = container_of(a, struct iomap_ioend, io_list); > struct iomap_ioend *ib = container_of(b, struct iomap_ioend, io_list); > diff --git a/include/linux/list_sort.h b/include/linux/list_sort.h > index 20f178c24e9d..4fe9cb94d0d1 100644 > --- a/include/linux/list_sort.h > +++ b/include/linux/list_sort.h > @@ -6,8 +6,9 @@ > > struct list_head; > > +typedef int __attribute__((nonnull(2,3))) (*cmp_func)(void *, > + struct list_head const *, struct list_head const *); > + Note that we already have cmp_func_t in linux/types.h, so something like list_cmp_func_t would probably be more appropriate here. > __attribute__((nonnull(2,3))) > -void list_sort(void *priv, struct list_head *head, > - int (*cmp)(void *priv, struct list_head *a, > - struct list_head *b)); > +void list_sort(void *priv, struct list_head *head, cmp_func cmp); > #endif > diff --git a/lib/list_sort.c b/lib/list_sort.c > index 52f0c258c895..6cfac649c4a6 100644 > --- a/lib/list_sort.c > +++ b/lib/list_sort.c > @@ -7,9 +7,6 @@ > #include <linux/list_sort.h> > #include <linux/list.h> > > -typedef int __attribute__((nonnull(2,3))) (*cmp_func)(void *, > - struct list_head const *, struct list_head const *); > - > /* > * Returns a list organized in an intermediate format suited > * to chaining of merge() calls: null-terminated, no reserved or > @@ -185,9 +182,7 @@ static void merge_final(void *priv, cmp_func cmp, > struct list_head *head, > * 2^(k+1) - 1 (second merge of case 5 when x == 2^(k-1) - 1). > */ > __attribute__((nonnull(2,3))) > -void list_sort(void *priv, struct list_head *head, > - int (*cmp)(void *priv, struct list_head *a, > - struct list_head *b)) > +void list_sort(void *priv, struct list_head *head, cmp_func cmp) > { > struct list_head *list = head->next, *pending = NULL; > size_t count = 0; /* Count of pending */ > ``` > There are probably more instances in the tree to clean up, but that > compiles with x86_64 defconfig, and I'm sure it doesn't suffer the CFI > issue from the cast. You indeed missed some callers, but after fixing all the remaining ones too, arm64 and x86_64 allyesconfigs still seem to build just fine for me: arch/arm64/kvm/vgic/vgic-its.c | 8 ++++---- arch/arm64/kvm/vgic/vgic.c | 2 +- block/blk-mq-sched.c | 2 +- block/blk-mq.c | 2 +- drivers/acpi/nfit/core.c | 2 +- drivers/acpi/numa/hmat.c | 2 +- drivers/clk/keystone/sci-clk.c | 4 ++-- drivers/gpu/drm/drm_modes.c | 2 +- drivers/gpu/drm/i915/gt/intel_engine_user.c | 2 +- drivers/gpu/drm/i915/gvt/debugfs.c | 2 +- drivers/gpu/drm/i915/selftests/i915_gem_gtt.c | 2 +- drivers/gpu/drm/radeon/radeon_cs.c | 4 ++-- drivers/infiniband/hw/usnic/usnic_uiom_interval_tree.c | 2 +- drivers/interconnect/qcom/bcm-voter.c | 2 +- drivers/md/raid5.c | 2 +- drivers/misc/sram.c | 4 ++-- drivers/nvme/host/core.c | 2 +- drivers/pci/controller/cadence/pcie-cadence-host.c | 3 ++- drivers/spi/spi-loopback-test.c | 2 +- fs/btrfs/raid56.c | 2 +- fs/btrfs/tree-log.c | 2 +- fs/btrfs/volumes.c | 2 +- fs/ext4/fsmap.c | 4 ++-- fs/gfs2/glock.c | 2 +- fs/gfs2/log.c | 2 +- fs/gfs2/lops.c | 2 +- fs/iomap/buffered-io.c | 2 +- fs/ubifs/gc.c | 6 +++--- fs/ubifs/replay.c | 4 ++-- fs/xfs/scrub/bitmap.c | 4 ++-- fs/xfs/xfs_bmap_item.c | 4 ++-- fs/xfs/xfs_buf.c | 4 ++-- fs/xfs/xfs_extent_busy.c | 4 ++-- fs/xfs/xfs_extent_busy.h | 2 +- fs/xfs/xfs_extfree_item.c | 4 ++-- fs/xfs/xfs_refcount_item.c | 4 ++-- fs/xfs/xfs_rmap_item.c | 4 ++-- include/linux/list_sort.h | 7 ++++--- lib/list_sort.c | 17 ++++++----------- lib/test_list_sort.c | 2 +- net/tipc/name_table.c | 4 ++-- 41 files changed, 68 insertions(+), 71 deletions(-) I'll have to double check that all the affected code is actually included in these builds, but if nobody objects and I don't run into any issues, I'll include the patch in v3. Sami
diff --git a/lib/list_sort.c b/lib/list_sort.c index 52f0c258c895..b14accf4ef83 100644 --- a/lib/list_sort.c +++ b/lib/list_sort.c @@ -8,7 +8,7 @@ #include <linux/list.h> typedef int __attribute__((nonnull(2,3))) (*cmp_func)(void *, - struct list_head const *, struct list_head const *); + struct list_head *, struct list_head *); /* * Returns a list organized in an intermediate format suited @@ -227,7 +227,7 @@ void list_sort(void *priv, struct list_head *head, if (likely(bits)) { struct list_head *a = *tail, *b = a->prev; - a = merge(priv, (cmp_func)cmp, b, a); + a = merge(priv, cmp, b, a); /* Install the merged result in place of the inputs */ a->prev = b->prev; *tail = a; @@ -249,10 +249,10 @@ void list_sort(void *priv, struct list_head *head, if (!next) break; - list = merge(priv, (cmp_func)cmp, pending, list); + list = merge(priv, cmp, pending, list); pending = next; } /* The final merge, rebuilding prev links */ - merge_final(priv, (cmp_func)cmp, head, pending, list); + merge_final(priv, cmp, head, pending, list); } EXPORT_SYMBOL(list_sort);
Casting the comparison function to a different type trips indirect call Control-Flow Integrity (CFI) checking. Remove the additional consts from cmp_func, and the now unneeded casts. Fixes: 043b3f7b6388 ("lib/list_sort: simplify and remove MAX_LIST_LENGTH_BITS") Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> --- lib/list_sort.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)