linux-kernel - Re: UBSAN: Undefined behaviour in block/blk-mq.c:1459:27 with pata

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Date:	Wed, 18 May 2016 09:59:11 +0300 (EEST)
From:	Meelis Roos <mroos@...ux.ee>
To:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
cc:	Linux Kernel list <linux-kernel@...r.kernel.org>,
	linux-ide@...r.kernel.org, linux-block@...r.kernel.org,
	Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>
Subject: Re: UBSAN: Undefined behaviour in block/blk-mq.c:1459:27 with
 pata_amd

> Does the patch below help?
> 
> From: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> Subject: [PATCH] blk-mq: fix undefined behaviour in order_to_size()
> 
> When this_order variable in blk_mq_init_rq_map() becomes zero
> the code incorrectly decrements the variable and passes the result
> to order_to_size() helper causing undefined behaviour:
> 
>  UBSAN: Undefined behaviour in block/blk-mq.c:1459:27
>  shift exponent 4294967295 is too large for 32-bit type 'unsigned int'
>  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0-rc6-00072-g33656a1 #22
> 
> Fix the code by checking this_order variable for not having the zero
> value first.
> 
> Reported-by: Meelis Roos <mroos@...ux.ee>
> Fixes: 320ae51feed5 ("blk-mq: new multi-queue block IO queueing mechanism")
> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>

It fixes the warning independently of the pata driver - ata_piix 
pata_via pata_serverworks pata_macio 3ware were fixed too.

-- 
Meelis Roos (mroos@...ux.ee)