This is a note to let you know that I've just added the patch titled
drm/dp_mst: Fix NULL deref in get_mst_branch_device_by_guid_helper()
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-dp_mst-fix-null-deref-in-get_mst_branch_device_b.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d8baf23c13cb3c590b2028d19db906ffba74122b
Author: Lukasz Majczak <lma@xxxxxxxxxxxx>
Date: Fri Sep 22 08:34:10 2023 +0200
drm/dp_mst: Fix NULL deref in get_mst_branch_device_by_guid_helper()
[ Upstream commit 3d887d512494d678b17c57b835c32f4e48d34f26 ]
As drm_dp_get_mst_branch_device_by_guid() is called from
drm_dp_get_mst_branch_device_by_guid(), mstb parameter has to be checked,
otherwise NULL dereference may occur in the call to
the memcpy() and cause following:
[12579.365869] BUG: kernel NULL pointer dereference, address: 0000000000000049
[12579.365878] #PF: supervisor read access in kernel mode
[12579.365880] #PF: error_code(0x0000) - not-present page
[12579.365882] PGD 0 P4D 0
[12579.365887] Oops: 0000 [#1] PREEMPT SMP NOPTI
...
[12579.365895] Workqueue: events_long drm_dp_mst_up_req_work
[12579.365899] RIP: 0010:memcmp+0xb/0x29
[12579.365921] Call Trace:
[12579.365927] get_mst_branch_device_by_guid_helper+0x22/0x64
[12579.365930] drm_dp_mst_up_req_work+0x137/0x416
[12579.365933] process_one_work+0x1d0/0x419
[12579.365935] worker_thread+0x11a/0x289
[12579.365938] kthread+0x13e/0x14f
[12579.365941] ? process_one_work+0x419/0x419
[12579.365943] ? kthread_blkcg+0x31/0x31
[12579.365946] ret_from_fork+0x1f/0x30
As get_mst_branch_device_by_guid_helper() is recursive, moving condition
to the first line allow to remove a similar one for step over of NULL elements
inside a loop.
Fixes: 5e93b8208d3c ("drm/dp/mst: move GUID storage from mgr, port to only mst branch")
Cc: <stable@xxxxxxxxxxxxxxx> # 4.14+
Signed-off-by: Lukasz Majczak <lma@xxxxxxxxxxxx>
Reviewed-by: Radoslaw Biernacki <rad@xxxxxxxxxxxx>
Signed-off-by: Manasi Navare <navaremanasi@xxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20230922063410.23626-1-lma@xxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index d02e323a4ecde..865c7f39143ec 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2615,14 +2615,14 @@ static struct drm_dp_mst_branch *get_mst_branch_device_by_guid_helper(
struct drm_dp_mst_branch *found_mstb;
struct drm_dp_mst_port *port;
+ if (!mstb)
+ return NULL;
+
if (memcmp(mstb->guid, guid, 16) == 0)
return mstb;
list_for_each_entry(port, &mstb->ports, next) {
- if (!port->mstb)
- continue;
-
found_mstb = get_mst_branch_device_by_guid_helper(port->mstb, guid);
if (found_mstb)
