[dm-devel] [PATCH] dm-snasphot: fix a crash if we have an origin with no snapshots

[Michael Tokarev]

07.05.2021 18:38, Mikulas Patocka wrote:
> If we have an origin target with no snapshots, o->split_boundary is set to 0.
> This causes BUG at block/bio.c:1474
> 
> This patch fixes the bug - if there are no snapshots, split_boundary is set
> to 0x80000000U.
> 
> Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
> Cc: stable at vger.kernel.org
> Reported-by: Michael Tokarev <mjt at tls.msk.ru>

Tested-by: Michael Tokarev <mjt at tls.msk.ru>

This eliminates the crash, and now things seem to work fine.
Thank you!

/mjt


> Index: linux-2.6/drivers/md/dm-snap.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/dm-snap.c
> +++ linux-2.6/drivers/md/dm-snap.c
> @@ -854,12 +854,11 @@ static int dm_add_exception(void *contex
>   static uint32_t __minimum_chunk_size(struct origin *o)
>   {
>   	struct dm_snapshot *snap;
> -	unsigned chunk_size = 0;
> +	unsigned chunk_size = 0x80000000U;
>   
>   	if (o)
>   		list_for_each_entry(snap, &o->snapshots, list)
> -			chunk_size = min_not_zero(chunk_size,
> -						  snap->store->chunk_size);
> +			chunk_size = min(chunk_size, snap->store->chunk_size);
>   
>   	return (uint32_t) chunk_size;
>   }
>