Re: [PATCH] s390/appldata: Fix error handling in appldata_generic_handler()

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

On Wed, Oct 21, 2026 at 02:04:26PM +0200, Gerald Schaefer wrote:
> appldata_generic_handler() always returns 0 after starting or stopping
> monitor recording.
> 
> So "echo {0,1} > /proc/sys/appldata/{os,mem,net_sum}" returns success even
> when DIAG 0xDC failed. A failed start would keep ops->active as 0, so
> reading the sysctl later would correctly reflect this.
> 
> A failed stop would falsely set ops->active to 0 and decrement module
> refcount. This would allow the data gathering module to be removed, and
> the data buffer to be freed, while z/VM monitor service is still collecting
> data from that buffer.
> 
> Fix this by returning -EIO when appldata_diag() failed, and only set
> ops->active to 0 and decrement module refcount when it succeeded on stop
> path.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
> ---
>  arch/s390/appldata/appldata_base.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)

Applied, thanks!