[Devel] [PATCH vz10] dm-ploop: return -ENOMEM (not ENOMEM) on mtfile allocation failure

[Vasileios Almpanis]

On 6/4/26 11:19 AM, Konstantin Khorenko wrote:

> In ploop_add_delta() the kcalloc() failure path for deltas[level].mtfile
> set a POSITIVE errno:
>
> 	if (!deltas[level].mtfile) {
> 		ret = ENOMEM;
> 		goto out;
> 	}
>
> The only caller, ploop_add_deltas_stack(), treats the result as an error
> with "if (ret < 0)", so a positive ENOMEM is not recognised as failure:
> the stack-setup loop completes and returns 0 (success) while
> deltas[level].mtfile stays NULL. Later IO paths then dereference
> mtfile[pio->runner_id] (e.g. in the per-runner submit path) and NULL-deref.
>
> Negate the value to -ENOMEM so the error is propagated.
>
> Fixes: 16b86ada6062 ("dm-ploop: use filp per thread")
> https://virtuozzo.atlassian.net/browse/VSTOR-132310
> Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>

Reviewed-by: Vasileios Almpanis <vasileios.almpanis at virtuozzo.com>

> ---
>   drivers/md/dm-ploop-bat.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/dm-ploop-bat.c b/drivers/md/dm-ploop-bat.c
> index 7746babf04a7..a7849de8aaa6 100644
> --- a/drivers/md/dm-ploop-bat.c
> +++ b/drivers/md/dm-ploop-bat.c
> @@ -507,7 +507,7 @@ int ploop_add_delta(struct ploop *ploop, u32 level, struct file *file, bool is_r
>   	deltas[level].mtfile = kcalloc(ploop->nkt_runners, sizeof(*file),
>   					GFP_KERNEL);
>   	if (!deltas[level].mtfile) {
> -		ret = ENOMEM;
> +		ret = -ENOMEM;
>   		goto out;
>   	}
>   	for (i = 0; i < ploop->nkt_runners; i++) {

-- 
Best regards, Vasileios Almpanis
Software Developer, Virtuozzo.