linux-kernel - Re: Patch "ata: sata_mv, avoid trigerrable BUG_ON" has been added to the 4.4-stable tree

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Date:   Mon, 28 Sep 2020 14:30:57 +0200
From:   Greg KH <greg@...ah.com>
To:     linux-kernel@...r.kernel.org
Cc:     jslaby@...e.cz, stable-commits@...r.kernel.org
Subject: Re: Patch "ata: sata_mv, avoid trigerrable BUG_ON" has been added to
 the 4.4-stable tree

On Sun, Sep 27, 2020 at 02:11:18PM -0400, Sasha Levin wrote:
> This is a note to let you know that I've just added the patch titled
> 
>     ata: sata_mv, avoid trigerrable BUG_ON
> 
> to the 4.4-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> The filename of the patch is:
>      ata-sata_mv-avoid-trigerrable-bug_on.patch
> and it can be found in the queue-4.4 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@...r.kernel.org> know about it.
> 
> 
> 
> commit 4b308d858a1a34dae1e38948f2c0497161d9ddd8
> Author: Jiri Slaby <jslaby@...e.cz>
> Date:   Thu Oct 31 10:59:46 2019 +0100
> 
>     ata: sata_mv, avoid trigerrable BUG_ON
>     
>     [ Upstream commit e9f691d899188679746eeb96e6cb520459eda9b4 ]
>     
>     There are several reports that the BUG_ON on unsupported command in
>     mv_qc_prep can be triggered under some circumstances:
>     https://bugzilla.suse.com/show_bug.cgi?id=1110252
>     https://serverfault.com/questions/888897/raid-problems-after-power-outage
>     https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1652185
>     https://bugs.centos.org/view.php?id=14998
>     
>     Let sata_mv handle the failure gracefully: warn about that incl. the
>     failed command number and return an AC_ERR_INVALID error. We can do that
>     now thanks to the previous patch.
>     
>     Remove also the long-standing FIXME.
>     
>     [v2] use %.2x as commands are defined as hexa.
>     
>     Signed-off-by: Jiri Slaby <jslaby@...e.cz>
>     Cc: Jens Axboe <axboe@...nel.dk>
>     Cc: linux-ide@...r.kernel.org
>     Cc: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
>     Signed-off-by: Jens Axboe <axboe@...nel.dk>
>     Signed-off-by: Sasha Levin <sashal@...nel.org>
> 
> diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
> index 729f26322095e..c24bbdb3f76c8 100644
> --- a/drivers/ata/sata_mv.c
> +++ b/drivers/ata/sata_mv.c
> @@ -2113,12 +2113,10 @@ static void mv_qc_prep(struct ata_queued_cmd *qc)
>  		 * non-NCQ mode are: [RW] STREAM DMA and W DMA FUA EXT, none
>  		 * of which are defined/used by Linux.  If we get here, this
>  		 * driver needs work.
> -		 *
> -		 * FIXME: modify libata to give qc_prep a return value and
> -		 * return error here.
>  		 */
> -		BUG_ON(tf->command);
> -		break;
> +		ata_port_err(ap, "%s: unsupported command: %.2x\n", __func__,
> +				tf->command);
> +		return AC_ERR_INVALID;
>  	}
>  	mv_crqb_pack_cmd(cw++, tf->nsect, ATA_REG_NSECT, 0);
>  	mv_crqb_pack_cmd(cw++, tf->hob_lbal, ATA_REG_LBAL, 0);

This causes a build warning as you can not return a value for a void
function :(

I'll drop it from the 4.4 queue now, thanks,

greg k-h