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McKenney" , Christoph Hellwig , bpf , linux-hardening@vger.kernel.org, linux-arch , Linux ARM , Linux Kbuild mailing list , PCI , LKML X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210318_183130_017398_949C9C25 X-CRM114-Status: GOOD ( 31.76 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Mar 18, 2021 at 10:11 AM Sami Tolvanen 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 > Reviewed-by: Kees Cook > --- > 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 > > 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 #include -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 > -- Thanks, ~Nick Desaulniers _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel