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Date: Sat, 14 May 2016 12:05:56 +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? Yes, the warning is gone and I see not other errors. There is nothing attached to pata_amd so I do not know if it works too. > > 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> > --- > block/blk-mq.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 0c2ed83..7df9c92 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -1495,7 +1495,7 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set, > int to_do; > void *p; > > - while (left < order_to_size(this_order - 1) && this_order) > + while (this_order && left < order_to_size(this_order - 1)) > this_order--; > > do { > -- Meelis Roos (mroos@...ux.ee)
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