diff options
| author | Dmitry Antipov <dmantipov@yandex.ru> | 2024-02-09 15:52:19 +0300 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2024-02-12 11:00:10 +0100 |
| commit | d0089603fa7a22a940f808a7cbc49402fe02281e (patch) | |
| tree | be5ce0f7dd511f1b6f3bd31be9a1c9fc03a8edfb /fs/fcntl.c | |
| parent | ef560389ca50e33bd0c4531236c187107fa81e1f (diff) | |
fs: prefer kfree_rcu() in fasync_remove_entry()
In 'fasync_remove_entry()', prefer 'kfree_rcu()' over 'call_rcu()' with dummy
'fasync_free_rcu()' callback. This is mostly intended in attempt to fix weird
https://syzkaller.appspot.com/bug?id=6a64ad907e361e49e92d1c4c114128a1bda2ed7f,
where kmemleak may consider 'fa' as unreferenced during RCU grace period. See
https://lore.kernel.org/stable/20230930174657.800551-1-joel@joelfernandes.org
as well. Comments are highly appreciated.
Ever since ae65a5211d90 ("mm/slab: document kfree() as allowed for
kmem_cache_alloc() objects") kfree() can be used for both kmalloc() and
kmem_cache_alloc() so this is no safe.
Do not backport this to stable, please.
Link ae65a5211d90 ("mm/slab: document kfree() as > allowed for kmem_cache_alloc() objects")
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Link: https://lore.kernel.org/r/20240209125220.330383-1-dmantipov@yandex.ru
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/fcntl.c')
| -rw-r--r-- | fs/fcntl.c | 8 |
1 files changed, 1 insertions, 7 deletions
diff --git a/fs/fcntl.c b/fs/fcntl.c index c80a6acad742..c3e342eb74af 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -846,12 +846,6 @@ int send_sigurg(struct fown_struct *fown) static DEFINE_SPINLOCK(fasync_lock); static struct kmem_cache *fasync_cache __ro_after_init; -static void fasync_free_rcu(struct rcu_head *head) -{ - kmem_cache_free(fasync_cache, - container_of(head, struct fasync_struct, fa_rcu)); -} - /* * Remove a fasync entry. If successfully removed, return * positive and clear the FASYNC flag. If no entry exists, @@ -877,7 +871,7 @@ int fasync_remove_entry(struct file *filp, struct fasync_struct **fapp) write_unlock_irq(&fa->fa_lock); *fp = fa->fa_next; - call_rcu(&fa->fa_rcu, fasync_free_rcu); + kfree_rcu(fa, fa_rcu); filp->f_flags &= ~FASYNC; result = 1; break; |