linux-kernel - Re: [PATCH] scsi: fix random memory corruption with scsi-mq + T10 PI

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Date:	Thu, 11 Dec 2014 14:18:22 -0800
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	Tony Battersby <tonyb@...ernetics.com>
Cc:	linux-scsi@...r.kernel.org,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] scsi: fix random memory corruption with scsi-mq + T10 PI

Hi Tony,

On Mon, 2014-12-08 at 17:20 -0500, Tony Battersby wrote:
> This fixes random memory corruption triggered when all three of the
> following are true:
> 
> * scsi-mq enabled
> * T10 Protection Information (DIF) enabled
> * SCSI host with sg_tablesize > SCSI_MAX_SG_SEGMENTS (128)
> 
> The symptoms of this bug are unpredictable memory corruption, BUG()s,
> oopses, lockups, etc., any of which may appear to be completely
> unrelated to the root cause.
> 
> Cc: <stable@...r.kernel.org> # 3.17.x, 3.18.x
> Signed-off-by: Tony Battersby <tonyb@...ernetics.com>
> 
> ---
> 
> I encountered this problem with a QLogic QLE2672 FC HBA using qla2xxx.
> On my system, this would trigger BUG_ON(atomic_read(&bio->bi_remaining) <= 0)
> in bio_endio(), or a general protection fault in __sg_free_table()
> trying to free prot_sdb, or any number of other weird random problems.
> All of this was caused by cmd->prot_sdb pointing to the wrong memory.
> To see how the memory is allocated, refer to scsi_mq_setup_tags() in
> scsi_lib.c.
> 
> For inclusion in 3.19, 3.18.x, and 3.17.x.
> 
> --- linux-3.18.0/drivers/scsi/scsi_lib.c.orig	2014-12-08 16:23:28.000000000 -0500
> +++ linux-3.18.0/drivers/scsi/scsi_lib.c	2014-12-08 16:24:00.000000000 -0500
> @@ -1829,7 +1829,9 @@ static int scsi_mq_prep_fn(struct reques
>  
>  	if (scsi_host_get_prot(shost)) {
>  		cmd->prot_sdb = (void *)sg +
> -			shost->sg_tablesize * sizeof(struct scatterlist);
> +			min_t(unsigned int,
> +			      shost->sg_tablesize, SCSI_MAX_SG_SEGMENTS) *
> +			sizeof(struct scatterlist);
>  		memset(cmd->prot_sdb, 0, sizeof(struct scsi_data_buffer));
>  
>  		cmd->prot_sdb->table.sgl =
> 

Nice catch.

Reviewed-by: Nicholas Bellinger <nab@...ux-iscsi.org>

Adding a CC' to MKP, and HCH so he can pick it up.

--nab

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