[PATCH 5.15 017/164] s390/cio: Fix device lifecycle handling in css_alloc_subchannel()

Sasha Levin
2026-02-28T18:15:20Z

From: Salah Triki <salah.triki@gmail.com>

[ Upstream commit f65c75b0b9b5a390bc3beadcde0a6fbc3ad118f7 ]

`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@gmail.com>
Reviewed-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 3c499136af657..4c3fde0bd5512 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -247,7 +247,7 @@ struct subchannel *css_alloc_subchannel(struct subchannel_id schid,
err_lock:
kfree(sch->lock);
err:
- kfree(sch);
+ put_device(&sch->dev);
return ERR_PTR(ret);
}

--
2.51.0