block: check if zone_wplugs_hash exists in queue_zone_wplugs_show

Changhui reported a kernel crash when running this simple shell reproducer: # cd /sys/kernel/debug/block && find . -type f -exec grep -aH . {} \; The above results in a NULL pointer dereference if a device does not have a zone_wplugs_hash allocated. To fix this, return early if we don't have a zone_wplugs_hash. Reported-by: Changhui Zhong <[email protected]> Fixes: a98b05b ("block: Replace zone_wlock debugfs entry with zone_wplugs entry") Signed-off-by: Johannes Thumshirn <[email protected]> Reviewed-by: Damien Le Moal <[email protected]> Link: https://lore.kernel.org/r/e5fec079dfca448cc21c425cfa5d7b291f5faa67.1714046443.git.johannes.thumshirn@wdc.com Signed-off-by: Jens Axboe <[email protected]>
sedwards · Apr 25, 2024 · 57787fa · 57787fa
1 parent a8f59e5
commit 57787fa
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/block/blk-zoned.c b/block/blk-zoned.c
@@ -1774,6 +1774,9 @@ int queue_zone_wplugs_show(void *data, struct seq_file *m)
 	unsigned int zwp_bio_list_size, i;
 	unsigned long flags;
 
+	if (!disk->zone_wplugs_hash)
+		return 0;
+
 	rcu_read_lock();
 	for (i = 0; i < disk_zone_wplugs_hash_size(disk); i++) {
 		hlist_for_each_entry_rcu(zwplug,