On Thu, Apr 25, 2024 at 8:02 PM Johannes Thumshirn
<johannes.thumshirn@xxxxxxx> wrote:
>
> 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 <czhong@xxxxxxxxxx>
> Fixes: a98b05b02f0f ("block: Replace zone_wlock debugfs entry with zone_wplugs entry")
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
> ---
> block/blk-zoned.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 3a796420f240..bad68277c0b2 100644
> --- 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,
> --
> 2.43.0
>
>
Verified the panic issue was fixed by this patch,
Tested-by: Changhui Zhong <czhong@xxxxxxxxxx>
