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

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Message-ID: <20260130204800.217395-1-salah.triki@gmail.com>
Date: Fri, 30 Jan 2026 21:47:59 +0100
From: Salah Triki <salah.triki@...il.com>
To: Vineeth Vijayan <vneethv@...ux.ibm.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,
	Salah Triki <salah.triki@...il.com>
Subject: [PATCH] s390/cio: fix device lifecycle handling in css_alloc_subchannel()

`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>
---
 drivers/s390/cio/css.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index 4c85df7a548e..ac24e019020e 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -235,7 +235,7 @@ struct subchannel *css_alloc_subchannel(struct subchannel_id schid,
 	return sch;

 err:
-	kfree(sch);
+	put_device(&sch->dev);
 	return ERR_PTR(ret);
 }

-- 
2.43.0