linux-kernel - Re: [PATCH] workqueue: Fix UBSAN 'subtraction overflow' error in shift_and

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Message-ID: <Zqlc6V0ZE6u9IgOu@slm.duckdns.org>
Date: Tue, 30 Jul 2024 11:36:41 -1000
From: Tejun Heo <tj@...nel.org>
To: Will Deacon <will@...nel.org>
Cc: linux-kernel@...r.kernel.org, Lai Jiangshan <jiangshanlai@...il.com>
Subject: Re: [PATCH] workqueue: Fix UBSAN 'subtraction overflow' error in
 shift_and_mask()

On Tue, Jul 30, 2024 at 12:44:31PM +0100, Will Deacon wrote:
...
> This is due to shift_and_mask() using a signed immediate to construct
> the mask and being called with a shift of 31 (WORK_OFFQ_POOL_SHIFT) so
> that it ends up decrementing from INT_MIN.
> 
> Use an unsigned constant '1U' to generate the mask in shift_and_mask().
> 
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Lai Jiangshan <jiangshanlai@...il.com>
> Fixes: 1211f3b21c2a ("workqueue: Preserve OFFQ bits in cancel[_sync] paths")
> Signed-off-by: Will Deacon <will@...nel.org>

Applied to wq/for-6.11-fixes.

Thanks.

-- 
tejun