[PATCH 6.18 1007/1611] afs: Fix missing NULL pointer check in afs_break_some_callbacks()

[Greg Kroah-Hartman]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Howells <dhowells at redhat.com>

[ Upstream commit 794a01110390c1b76f59ece773fb0fbfd89c6f5c ]

Fix afs_break_some_callbacks() to check to see if afs_lookup_volume_rcu()
returned NULL (e.g. the specified volume is unknown).

Fixes: 8230fd8217b7 ("afs: Make callback processing more efficient.")
Closes: https://sashiko.dev/#/patchset/20260609081738.770127-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells at redhat.com>
Link: https://patch.msgid.link/20260622090856.2746629-16-dhowells@redhat.com
cc: Marc Dionne <marc.dionne at auristor.com>
cc: linux-afs at lists.infradead.org
Signed-off-by: Christian Brauner (Amutable) <brauner at kernel.org>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 fs/afs/callback.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index 833ac3178ddc75..0a09a9ca3c6b37 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -220,7 +220,11 @@ static void afs_break_some_callbacks(struct afs_server *server,
 
 	rcu_read_lock();
 	volume = afs_lookup_volume_rcu(server->cell, vid);
-	if (cbb->fid.vnode == 0 && cbb->fid.unique == 0) {
+	if (!volume) {
+		/* Ignore breaks on unknown volumes. */
+		rcu_read_unlock();
+		*_count = 0;
+	} else if (cbb->fid.vnode == 0 && cbb->fid.unique == 0) {
 		afs_break_volume_callback(server, volume);
 		*_count -= 1;
 		if (*_count)
-- 
2.53.0