Christian Brauner 4e32c25b58 libfs: fix get_stashed_dentry() ...

get_stashed_dentry() tries to optimistically retrieve a stashed dentry
from a provided location.  It needs to ensure to hold rcu lock before it
dereference the stashed location to prevent UAF issues.  Use
rcu_dereference() instead of READ_ONCE() it's effectively equivalent
with some lockdep bells and whistles and it communicates clearly that
this expects rcu protection.

Link: https://lore.kernel.org/r/20240906-vfs-hotfix-5959800ffa68@brauner
Fixes: 07fd7c3298 ("libfs: add path_from_stashed()")
Reported-by: syzbot+f82b36bffae7ef78b6a7@syzkaller.appspotmail.com
Fixes: syzbot+f82b36bffae7ef78b6a7@syzkaller.appspotmail.com
Reported-by: syzbot+cbe4b96e1194b0e34db6@syzkaller.appspotmail.com
Fixes: syzbot+cbe4b96e1194b0e34db6@syzkaller.appspotmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2024-09-06 11:08:58 -07:00

59 KiB

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