czw., 3 sie 2023 o 11:23 Lukasz Majczak <lma@xxxxxxxxxxxx> napisał(a):
>
> Check mgr->mst_primary, before passing it to
> the get_mst_branch_device_by_guid_helper(), otherwise NULL dereference
> may occur in the call to memcpy() and cause:
>
> [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
>
> Similar check is done in e.g: drm_dp_mst_topology_get_mstb_validated().
>
> 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>
> ---
> drivers/gpu/drm/display/drm_dp_mst_topology.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 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..703cd97b1d11 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -2595,19 +2595,19 @@ static struct drm_dp_mst_branch *
> drm_dp_get_mst_branch_device_by_guid(struct drm_dp_mst_topology_mgr *mgr,
> const uint8_t *guid)
> {
> - struct drm_dp_mst_branch *mstb;
> + struct drm_dp_mst_branch *mstb = NULL;
> int ret;
>
> /* find the port by iterating down */
> mutex_lock(&mgr->lock);
> -
> - mstb = get_mst_branch_device_by_guid_helper(mgr->mst_primary, guid);
> - if (mstb) {
> - ret = drm_dp_mst_topology_try_get_mstb(mstb);
> - if (!ret)
> - mstb = NULL;
> + if (mgr->mst_primary) {
> + mstb = get_mst_branch_device_by_guid_helper(mgr->mst_primary, guid);
> + if (mstb) {
> + ret = drm_dp_mst_topology_try_get_mstb(mstb);
> + if (!ret)
> + mstb = NULL;
> + }
> }
> -
> mutex_unlock(&mgr->lock);
> return mstb;
> }
> --
> 2.41.0.640.ga95def55d0-goog
>
Hi,
Is there anything more I should do regarding these changes?
Best regards,
Lukasz
