[PATCH 2/3] s390/dasd: Fix wrong free and refcount leak in build_check_tcw error path

[Stefan Haberland <sth@linux.ibm.com>]

dasd_eckd_build_check_tcw() allocates its request with
dasd_fmalloc_request(), but its out_err path frees it with
dasd_sfree_request(). The latter uses a different pool and therefor,
leading to invalid pointer arithmetic and a crash.
Use the matching dasd_ffree_request() instead.

The same error path also leaves start_priv->count incremented
without ever decrementing it again.
This leaks a permanent reference on every build failure.
Decrement it before freeing the request.

Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260722103704.1709668-1-sth@linux.ibm.com
Fixes: 8fd575200db5 ("s390/dasd: Add new ioctl BIODASDCHECKFMT")
Cc: stable@vger.kernel.org #4.7
Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
---
 drivers/s390/block/dasd_eckd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
index e910d6b35f0f..687350504c3e 100644
--- a/drivers/s390/block/dasd_eckd.c
+++ b/drivers/s390/block/dasd_eckd.c
@@ -2764,7 +2764,8 @@ dasd_eckd_build_check_tcw(struct dasd_device *base, struct format_data_t *fdata,
 	return cqr;
 
 out_err:
-	dasd_sfree_request(cqr, startdev);
+	start_priv->count--;
+	dasd_ffree_request(cqr, startdev);
 
 	return ERR_PTR(rc);
 }
-- 
2.53.0