wt., 26 wrz 2023 o 16:01 Radosław Biernacki rad@chromium.org napisał(a):
On Fri, Sep 22, 2023 at 8:34 AM Lukasz Majczak lma@semihalf.com wrote:
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@vger.kernel.org # 4.14+ Signed-off-by: Lukasz Majczak lma@semihalf.com
v2->v3:
- Fixed patch description.
drivers/gpu/drm/display/drm_dp_mst_topology.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c index ed96cfcfa304..8c929ef72c72 100644 --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c @@ -2574,14 +2574,14 @@ 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)-- 2.42.0.515.g380fc7ccd1-goog
Reviewed-by: Radoslaw Biernacki rad@chromium.org
Hi,
Is there anything more I should do with this patch?
Thanks, Lukasz