FAILED: patch "[PATCH] s390/vmcp: Initialize full session info to zero" failed to apply to 5.15-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x f63eb4ee4a30fc5d8de07a229d92310e3c8d560c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107060217-failed-5.15-f63eb4ee4a30@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From f63eb4ee4a30fc5d8de07a229d92310e3c8d560c Mon Sep 17 00:00:00 2001
From: Christian Borntraeger <borntraeger@linux.ibm.com>
Date: Tue, 29 Sep 2026 15:58:29 +0200
Subject: [PATCH] s390/vmcp: Initialize full session info to zero

The cma_alloc bit as well as the response can contain old data.
cma_release will not free the kmalloced memory in that case and
the response code might leak kernel stack data to CAP_SYS_ADMIN
users.

Cc: stable@vger.kernel.org
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 drivers/s390/char/vmcp.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/s390/char/vmcp.c b/drivers/s390/char/vmcp.c
index b277f9d0c321a..2cf94f23af2a6 100644
--- a/drivers/s390/char/vmcp.c
+++ b/drivers/s390/char/vmcp.c
@@ -104,13 +104,11 @@ static int vmcp_open(struct inode *inode, struct file *file)
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	session = kmalloc_obj(*session);
+	session = kzalloc_obj(*session);
 	if (!session)
 		return -ENOMEM;
 
 	session->bufsize = PAGE_SIZE;
-	session->response = NULL;
-	session->resp_size = 0;
 	mutex_init(&session->mutex);
 	file->private_data = session;
 	return nonseekable_open(inode, file);
-- 
2.53.0