[PATCH v4 15/21] afs: Fix missing NULL pointer check in afs_break_some_callbacks()

[David Howells]

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>
cc: Marc Dionne <marc.dionne at auristor.com>
cc: linux-afs at lists.infradead.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 dd7a407ea368..74853e0d0435 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -213,7 +213,11 @@ 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)