Re: [PATCH] s390/cio: fix device lifecycle handling in css_alloc_subchannel()

[Heiko Carstens <hca@linux.ibm.com>]

On Fri, Jan 30, 2026 at 09:47:59PM +0100, 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@gmail.com>
> ---
>  drivers/s390/cio/css.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks.