linux-kernel - Re: [PATCH] EDAC: Fix global-out-of-bounds write when setting edac_mc_poll

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Date:   Thu, 27 Jun 2019 18:11:18 +0100
From:   James Morse <james.morse@....com>
To:     Eiichi Tsukata <devel@...ukata.com>
Cc:     bp@...en8.de, mchehab@...nel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org, Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH] EDAC: Fix global-out-of-bounds write when setting
 edac_mc_poll_msec

Hello,

(CC: +Tony Luck.
 Original Patch: lore.kernel.org/r/20190626054011.30044-1-devel@...ukata.com )

On 26/06/2019 06:40, Eiichi Tsukata wrote:
> Commit 9da21b1509d8 ("EDAC: Poll timeout cannot be zero, p2") assumes
> edac_mc_poll_msec to be unsigned long, but the type of the variable still
> remained as int. Setting edac_mc_poll_msec can trigger out-of-bounds
> write.

Thanks for catching this!


> Fix it by changing the type of edac_mc_poll_msec to unsigned int.

This means reverting more of 9da21b1509d8, but it also fixes signed/unsigned issues:
| root@...ian-guest:/sys/module/edac_core/parameters# echo 4294967295 >  edac_mc_poll_msec
| root@...ian-guest:/sys/module/edac_core/parameters# cat edac_mc_poll_msec
| -1
| root@...ian-guest:/sys/module/edac_core/parameters# echo -1 > edac_mc_poll_msec
| -bash: echo: write error: Invalid argument


> The reason why this patch adopts unsigned int rather than unsigned long
> is msecs_to_jiffies() assumes arg to be unsigned int.

Ah, so the range is limited anyway.

It looks like it was switched to long to be consistent with edac_mc_workq_setup(), which
has since been removed in preference to msecs_to_jiffies().


Reviewed-by: James Morse <james.morse@....com>


Thanks,

James