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authorDmitry Antipov <dmantipov@yandex.ru>2024-02-09 15:52:19 +0300
committerChristian Brauner <brauner@kernel.org>2024-02-12 13:00:10 +0300
commitd0089603fa7a22a940f808a7cbc49402fe02281e (patch)
treebe5ce0f7dd511f1b6f3bd31be9a1c9fc03a8edfb /fs/fcntl.c
parentef560389ca50e33bd0c4531236c187107fa81e1f (diff)
downloadlinux-d0089603fa7a22a940f808a7cbc49402fe02281e.tar.xz
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.c8
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;