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SubjectRe: UBSAN: Undefined behaviour in block/blk-mq.c:1459:27 with pata_amd
> Does the patch below help?
>
> From: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.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@linux.ee>
> Fixes: 320ae51feed5 ("blk-mq: new multi-queue block IO queueing mechanism")
> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.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@linux.ee)

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