FAILED: patch "[PATCH] drm/panthor: validate userspace queue count against initialized firmware slot count" failed to apply to 7.3-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 7.3-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-7.3.y
git checkout FETCH_HEAD
git cherry-pick -x 00d4e932258fc5f2ace62daac307bd903ee400f5
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107050350-failed-7.3-00d4e932258f@kernel.org' --subject-prefix 'PATCH 7.3.y' 'HEAD^..'

Thanks,
Sasha

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

From 00d4e932258fc5f2ace62daac307bd903ee400f5 Mon Sep 17 00:00:00 2001
From: Osama Abdelkader <osama.abdelkader@gmail.com>
Date: Tue, 4 Aug 2026 18:00:47 +0200
Subject: [PATCH] drm/panthor: validate userspace queue count against
 initialized firmware slot count

In panthor_drv.c:panthor_ioctl_group_create(),
the queue count is validated against the hardcoded maximum:

	if (!args->queues.count || args->queues.count > MAX_CS_PER_CSG)
		return -EINVAL;

However, if the firmware reports fewer slots than MAX_CS_PER_CSG,
panthor_fw_init_ifaces() will only initialize that smaller number of
stream interfaces.

If unprivileged userspace requests more queues than the firmware reported
(but no more than MAX_CS_PER_CSG), cs_slot_prog_locked() fetches an
uninitialized stream interface and may crash when dereferencing
cs_iface->input->ringbuf_base.

Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block")
Cc: stable@vger.kernel.org
Reported-by: sashiko-bot@kernel.org
Closes: https://sashiko.dev/#/patchset/20260803141149.68182-1-osama.abdelkader@gmail.com?part=1
Signed-off-by: Osama Abdelkader <osama.abdelkader@gmail.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patch.msgid.link/20260804160048.174148-1-osama.abdelkader@gmail.com
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
---
 drivers/gpu/drm/panthor/panthor_sched.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index ac6aee554820e..0493858e55d76 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -3652,6 +3652,9 @@ int panthor_group_create(struct panthor_file *pfile,
 	    hweight64(group_args->tiler_core_mask) < group_args->max_tiler_cores)
 		return -EINVAL;
 
+	if (group_args->queues.count > sched->cs_slot_count)
+		return -EINVAL;
+
 	group = kzalloc_obj(*group);
 	if (!group)
 		return -ENOMEM;
-- 
2.53.0