linux-kernel - Re: [PATCH] s390/cio: fix device lifecycle handling in css_alloc

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Message-ID: <1ab8cc09-5efb-4c7e-ba75-170e9b8d3815@linux.ibm.com>
Date: Wed, 4 Feb 2026 12:47:50 +0100
From: Vineeth Vijayan <vneethv@...ux.ibm.com>
To: Salah Triki <salah.triki@...il.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>
Cc: linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] s390/cio: fix device lifecycle handling in
 css_alloc_subchannel()



On 1/30/26 21:47, Salah Triki wrote:
> `css_alloc_subchannel()` calls `device_initialize()` before setting up
> the DMA masks. If `dma_set_coherent_mask()` or `dma_set_mask()` fails,
> the error path frees the subchannel structure directly, bypassing
> the device model reference counting.
> 
> Once `device_initialize()` has been called, the embedded struct device
> must be released via `put_device()`, allowing the release callback to
> free the container structure.
> 
> Fix the error path by dropping the initial device reference with
> `put_device()` instead of calling `kfree()` directly.
> 
> This ensures correct device lifetime handling and avoids potential
> use-after-free or double-free issues.
> 
> Fixes: e5dcf0025d7af ("s390/css: move subchannel lock allocation")
> 
> Signed-off-by: Salah Triki<salah.triki@...il.com>
> ---

Thank you.
this looks good to me.

Reviewed-by: Vineeth Vijayan <vneethv@...ux.ibm.com>