This is a note to let you know that I've just added the patch titled
cachefiles: add missing lock protection when polling
to the 6.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cachefiles-add-missing-lock-protection-when-polling.patch
and it can be found in the queue-6.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 2b2309ba4490d255735d2bda122e91c4cb6b3942
Author: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
Date: Fri Jun 28 14:29:30 2024 +0800
cachefiles: add missing lock protection when polling
[ Upstream commit cf5bb09e742a9cf6349127e868329a8f69b7a014 ]
Add missing lock protection in poll routine when iterating xarray,
otherwise:
Even with RCU read lock held, only the slot of the radix tree is
ensured to be pinned there, while the data structure (e.g. struct
cachefiles_req) stored in the slot has no such guarantee. The poll
routine will iterate the radix tree and dereference cachefiles_req
accordingly. Thus RCU read lock is not adequate in this case and
spinlock is needed here.
Fixes: b817e22b2e91 ("cachefiles: narrow the scope of triggering EPOLLIN events in ondemand mode")
Signed-off-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240628062930.2467993-10-libaokun@xxxxxxxxxxxxxxx
Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
Reviewed-by: Jia Zhu <zhujia.zj@xxxxxxxxxxxxx>
Reviewed-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
index 06cdf1a8a16f6..89b11336a8369 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -366,14 +366,14 @@ static __poll_t cachefiles_daemon_poll(struct file *file,
if (cachefiles_in_ondemand_mode(cache)) {
if (!xa_empty(&cache->reqs)) {
- rcu_read_lock();
+ xas_lock(&xas);
xas_for_each_marked(&xas, req, ULONG_MAX, CACHEFILES_REQ_NEW) {
if (!cachefiles_ondemand_is_reopening_read(req)) {
mask |= EPOLLIN;
break;
}
}
- rcu_read_unlock();
+ xas_unlock(&xas);
}
} else {
if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
