linux-kernel - Re: [PATCH] blk-iocost: Fix shift-out-of-bounds in iocg_kick

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Date: Wed, 10 Apr 2024 09:53:52 -1000
From: Tejun Heo <tj@...nel.org>
To: Breno Leitao <leitao@...ian.org>
Cc: Josef Bacik <josef@...icpanda.com>, Jens Axboe <axboe@...nel.dk>,
	leit@...a.com,
	"open list:CONTROL GROUP - BLOCK IO CONTROLLER (BLKIO)" <cgroups@...r.kernel.org>,
	"open list:CONTROL GROUP - BLOCK IO CONTROLLER (BLKIO)" <linux-block@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] blk-iocost: Fix shift-out-of-bounds in iocg_kick_delay()

Hello, Breno.

On Wed, Apr 10, 2024 at 12:36:41PM -0700, Breno Leitao wrote:
> When running iocg_kick_delay(), iocg->delay_at could be way behind "now",
> which causes a huge tdelta difference.
> 
> The tdelta value is used to shift some bits around, raising the
> following UBSAN splat:
> 
> 	UBSAN: shift-out-of-bounds in block/blk-iocost.c:1366:23
> 
> Debugging this, these are some values I got in my machine with 6.9-rc3.
> 
>  now = 3626064295
>  iocg->delay_at = 3275794093
> 
> Fix this by validating that the shift if valid, otherwise bail out,
> similarly to commit 2a427b49d029 ("blk-iocost: Fix an UBSAN
> shift-out-of-bounds warning")

Rik alreaady sent a fix:

  http://lkml.kernel.org/r/20240404123253.0f58010f@imladris.surriel.com

which got commited as beaa51b36012fad5a4d3c18b88a617aea7a9b96d.

Thanks.

-- 
tejun