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

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

[Sasha Levin]

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

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

[Liviu Dudau]

On Sat, Nov 07, 2026 at 05:03:50AM -0500, Sasha Levin wrote:
> 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

Hi Sasha,

The reason patch fails to apply is because it's already in that tree under
commit ec86c43dcfff68eab4db9bdafcd3e2b16e342e18. Steven merged the patch
through drm-misc-fixes while I was at XDC, not knowing that I've also merged
the patch through drm-misc-next. Hence the two commit SHAs for the same code.

Best regards,
Liviu


> 
> ------------------ 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
> 
> 
> 
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
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