Messages in this thread Patch in this message | | | Date | Wed, 20 Jul 2022 09:29:45 -0700 | From | Roman Gushchin <> | Subject | Re: [PATCH] mm: shrinkers: fix double kfree on shrinker name |
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On Wed, Jul 20, 2022 at 11:47:55PM +0900, Tetsuo Handa wrote: > syzbot is reporting double kfree() at free_prealloced_shrinker() [1], for > destroy_unused_super() calls free_prealloced_shrinker() even if > prealloc_shrinker() returned an error. Explicitly clear shrinker name > when prealloc_shrinker() called kfree(). > > Link: https://syzkaller.appspot.com/bug?extid=8b481578352d4637f510 [1] > Reported-by: syzbot <syzbot+8b481578352d4637f510@syzkaller.appspotmail.com> > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > Fixes: e33c267ab70de424 ("mm: shrinkers: provide shrinkers with names")
Hi Tetsuo!
Thank you for the fix! It looks good to me, however I think we should go a bit further and and zero shrinker->name in all 4 cases where shrinker->name is freed (an example code below).
Please, feel free to add my ack: Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Thanks!
--- mm/shrinker_debug.c | 1 + mm/vmscan.c | 9 +++++++-- 2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c index e5b40c43221d..b05295bab322 100644 --- a/mm/shrinker_debug.c +++ b/mm/shrinker_debug.c @@ -251,6 +251,7 @@ void shrinker_debugfs_remove(struct shrinker *shrinker) lockdep_assert_held(&shrinker_rwsem); kfree_const(shrinker->name); + shrinker->name = NULL; if (!shrinker->debugfs_entry) return; diff --git a/mm/vmscan.c b/mm/vmscan.c index 8fa03fb5c5c1..9e7d8db42918 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -647,8 +647,10 @@ int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...) return -ENOMEM; err = __prealloc_shrinker(shrinker); - if (err) + if (err) { kfree_const(shrinker->name); + shrinker->name = NULL; + } return err; } @@ -663,6 +665,7 @@ void free_prealloced_shrinker(struct shrinker *shrinker) { #ifdef CONFIG_SHRINKER_DEBUG kfree_const(shrinker->name); + shrinker->name = NULL; #endif if (shrinker->flags & SHRINKER_MEMCG_AWARE) { down_write(&shrinker_rwsem); @@ -707,8 +710,10 @@ int register_shrinker(struct shrinker *shrinker, const char *fmt, ...) return -ENOMEM; err = __register_shrinker(shrinker); - if (err) + if (err) { kfree_const(shrinker->name); + shrinker->name = NULL; + } return err; } #else -- 2.36.1
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