kernel/linux.git/drivers/gpu/drm/display, branch v6.6.149

drm/dp_mst: Handle torn-down topology gracefully in drm_dp_mst_topology_queue_probe()

2026-08-03T09:15:32+00:00

commit 613059875958e7b217b250ed14c3b189f9488421 upstream. A hotplug or link-loss event can tear down the MST topology (setting mgr->mst_state = false and mgr->mst_primary = NULL) concurrently with a caller invoking drm_dp_mst_topology_queue_probe(). Since the check is already performed under mgr->lock, the condition is not a programming error but a valid race -- the topology was valid when the caller decided to call this function, but was torn down before the lock was acquired. Replace the drm_WARN_ON() with a graceful early return. This eliminates spurious kernel warnings and the resulting compositor crashes observed when connecting/disconnecting DP MST monitors, while keeping the correct behavior of doing nothing when MST is not active. A drm_dbg_mst() trace is added so the skipped probe remains observable under MST debug logging. The existing WARN_ON(mgr->mst_primary) in drm_dp_mst_topology_mgr_set_mst() already catches the case where the topology is initialized twice, so no diagnostic coverage is lost. Fixes: dbaeef363ea5 ("drm/dp_mst: Add a helper to queue a topology probe") Cc: Imre Deak Cc: Lyude Paul Cc: stable@vger.kernel.org Cc: intel-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org Signed-off-by: Jonas Emilsson Signed-off-by: Luca Coelho Link: https://lore.kernel.org/all/20260503034533.1023686-1-jonas.emilsson@gmail.com Acked-by: Imre Deak Link: https://patch.msgid.link/20260622140532.526722-1-luciano.coelho@intel.com Signed-off-by: Maarten Lankhorst Signed-off-by: Greg Kroah-Hartman

drm/dp/mst: fix OOB reads on 2-byte fields in sideband reply parsers

2026-08-03T09:15:23+00:00

commit 6b89ba3dba2f583626fb693e47e951ffb8bf591f upstream. Three sideband reply parsers read 16-bit fields as: val = (raw->msg[idx] << 8) | (raw->msg[idx+1]); and check bounds only after the fact. When idx == raw->curlen, raw->msg[idx+1] reads one byte past the received message data into the following struct fields (curchunk_len, curchunk_idx, curlen). Affected functions: - drm_dp_sideband_parse_enum_path_resources_ack() full_payload_bw_number and avail_payload_bw_number fields - drm_dp_sideband_parse_allocate_payload_ack() allocated_pbn field - drm_dp_sideband_parse_query_payload_ack() allocated_pbn field Fix by using a single combined check (idx + 2 > curlen) before each 2-byte read. Since the check is strictly tighter than idx > curlen, no separate step is needed. Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: # v3.17+ Signed-off-by: Ashutosh Desai Reviewed-by: Lyude Paul [added fixes tag] Signed-off-by: Lyude Paul Link: https://patch.msgid.link/20260510203128.2884846-1-ashutoshdesai993@gmail.com Signed-off-by: Greg Kroah-Hartman

drm/dp/mst: fix buffer overflows in sideband chunk accumulation

2026-08-03T09:15:23+00:00

commit 55bd5e685bda455b9b50c835f8c8442d52a344a3 upstream. drm_dp_sideband_append_payload() has three related bugs when processing device-provided sideband reply data: 1. Zero-length curchunk_len underflow: msg_len is a 6-bit field taken directly from the DP sideband header. If a device sends msg_len=0, curchunk_len is set to zero. The condition (curchunk_idx >= curchunk_len) is immediately true, and curchunk_len-1 wraps to 255 (u8 underflow). drm_dp_msg_data_crc4() reads 255 bytes from chunk[48], then memcpy() writes 255 bytes into msg[], both far out of bounds. 2. chunk[48] overflow: curchunk_len can reach 63 (6-bit field). chunk[] is only 48 bytes. Multi-iteration payload assembly appends 16-byte blocks until curchunk_idx reaches curchunk_len, writing up to 15 bytes past the end of chunk[] into msg[]. 3. msg[256] overflow: each chunk contributes (curchunk_len-1) bytes to msg[]. No check ensures curlen + (curchunk_len-1) stays within msg[256], so the memcpy can spill into adjacent struct fields. All three are reachable from any DP MST device that can forge sideband reply messages on a physical connection. Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: # v3.17+ Signed-off-by: Ashutosh Desai Reviewed-by: Lyude Paul Signed-off-by: Lyude Paul Link: https://patch.msgid.link/20260410041901.2438960-1-ashutoshdesai993@gmail.com Signed-off-by: Greg Kroah-Hartman

drm/dp/mst: fix OOB reads in remote DPCD/I2C sideband reply parsers

2026-08-03T09:15:23+00:00

commit 1a8f537f5a1eeac941f262fe73078d6b08ba83c0 upstream. drm_dp_sideband_parse_remote_dpcd_read() reads num_bytes from the raw message and then unconditionally does: memcpy(bytes, &raw->msg[idx], num_bytes); without checking that idx + num_bytes <= raw->curlen. raw->msg[] is 256 bytes; if a malicious or misbehaving MST hub sets num_bytes larger than the remaining payload, the memcpy reads past the received data into whatever follows in raw->msg[]. drm_dp_sideband_parse_remote_i2c_read_ack() has the same flaw (noted with a /* TODO check */ comment since the code was introduced). Fix both functions by using a single combined check (idx + num_bytes > curlen) before each memcpy. Since num_bytes is u8, it is always >= 0, so this strictly subsumes the simpler idx > curlen form and no separate step is needed. Fixes: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: # v3.17+ Signed-off-by: Ashutosh Desai Reviewed-by: Lyude Paul [added missing fixes tag] Signed-off-by: Lyude Paul Link: https://patch.msgid.link/20260510201733.2882224-1-ashutoshdesai993@gmail.com Signed-off-by: Greg Kroah-Hartman

drm/display/dp_mst: Add protection against 0 vcpi

2026-03-04T12:20:37+00:00

[ Upstream commit 342ccffd9f77fc29fe1c05fd145e4d842bd2feaa ] When releasing a timeslot there is a slight chance we may end up with the wrong payload mask due to overflow if the delayed_destroy_work ends up coming into play after a DP 2.1 monitor gets disconnected which causes vcpi to become 0 then we try to make the payload = ~BIT(vcpi - 1) which is a negative shift. VCPI id should never really be 0 hence skip changing the payload mask if VCPI is 0. Otherwise it leads to <7> [515.287237] xe 0000:03:00.0: [drm:drm_dp_mst_get_port_malloc [drm_display_helper]] port ffff888126ce9000 (3) <4> [515.287267] -----------[ cut here ]----------- <3> [515.287268] UBSAN: shift-out-of-bounds in ../drivers/gpu/drm/display/drm_dp_mst_topology.c:4575:36 <3> [515.287271] shift exponent -1 is negative <4> [515.287275] CPU: 7 UID: 0 PID: 3108 Comm: kworker/u64:33 Tainted: G S U 6.17.0-rc6-lgci-xe-xe-3795-3e79699fa1b216e92+ #1 PREEMPT(voluntary) <4> [515.287279] Tainted: [S]=CPU_OUT_OF_SPEC, [U]=USER <4> [515.287279] Hardware name: ASUS System Product Name/PRIME Z790-P WIFI, BIOS 1645 03/15/2024 <4> [515.287281] Workqueue: drm_dp_mst_wq drm_dp_delayed_destroy_work [drm_display_helper] <4> [515.287303] Call Trace: <4> [515.287304] <4> [515.287306] dump_stack_lvl+0xc1/0xf0 <4> [515.287313] dump_stack+0x10/0x20 <4> [515.287316] __ubsan_handle_shift_out_of_bounds+0x133/0x2e0 <4> [515.287324] ? drm_atomic_get_private_obj_state+0x186/0x1d0 <4> [515.287333] drm_dp_atomic_release_time_slots.cold+0x17/0x3d [drm_display_helper] <4> [515.287355] mst_connector_atomic_check+0x159/0x180 [xe] <4> [515.287546] drm_atomic_helper_check_modeset+0x4d9/0xfa0 <4> [515.287550] ? __ww_mutex_lock.constprop.0+0x6f/0x1a60 <4> [515.287562] intel_atomic_check+0x119/0x2b80 [xe] <4> [515.287740] ? find_held_lock+0x31/0x90 <4> [515.287747] ? lock_release+0xce/0x2a0 <4> [515.287754] drm_atomic_check_only+0x6a2/0xb40 <4> [515.287758] ? drm_atomic_add_affected_connectors+0x12b/0x140 <4> [515.287765] drm_atomic_commit+0x6e/0xf0 <4> [515.287766] ? _pfx__drm_printfn_info+0x10/0x10 <4> [515.287774] drm_client_modeset_commit_atomic+0x25c/0x2b0 <4> [515.287794] drm_client_modeset_commit_locked+0x60/0x1b0 <4> [515.287795] ? mutex_lock_nested+0x1b/0x30 <4> [515.287801] drm_client_modeset_commit+0x26/0x50 <4> [515.287804] __drm_fb_helper_restore_fbdev_mode_unlocked+0xdc/0x110 <4> [515.287810] drm_fb_helper_hotplug_event+0x120/0x140 <4> [515.287814] drm_fbdev_client_hotplug+0x28/0xd0 <4> [515.287819] drm_client_hotplug+0x6c/0xf0 <4> [515.287824] drm_client_dev_hotplug+0x9e/0xd0 <4> [515.287829] drm_kms_helper_hotplug_event+0x1a/0x30 <4> [515.287834] drm_dp_delayed_destroy_work+0x3df/0x410 [drm_display_helper] <4> [515.287861] process_one_work+0x22b/0x6f0 <4> [515.287874] worker_thread+0x1e8/0x3d0 <4> [515.287879] ? __pfx_worker_thread+0x10/0x10 <4> [515.287882] kthread+0x11c/0x250 <4> [515.287886] ? __pfx_kthread+0x10/0x10 <4> [515.287890] ret_from_fork+0x2d7/0x310 <4> [515.287894] ? __pfx_kthread+0x10/0x10 <4> [515.287897] ret_from_fork_asm+0x1a/0x30 Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6303 Signed-off-by: Suraj Kandpal Reviewed-by: Imre Deak Reviewed-by: Lyude Paul Link: https://patch.msgid.link/20251119094650.799135-1-suraj.kandpal@intel.com Signed-off-by: Sasha Levin

Revert "drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS"

2025-09-04T13:30:29+00:00

This reverts commit 65e46aeaf84aa88539bcff6b8077e05fbd0700da which is commit a40c5d727b8111b5db424a1e43e14a1dcce1e77f upstream. The upstream commit a40c5d727b8111b5db424a1e43e14a1dcce1e77f ("drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS") the reverted commit backported causes a regression, on one eDP panel at least resulting in display flickering, described in detail at the Link: below. The issue fixed by the upstream commit will need a different solution, revert the backport for now. Cc: intel-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org Cc: Sasha Levin Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14558 Signed-off-by: Imre Deak Signed-off-by: Greg Kroah-Hartman

drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS

2025-08-28T14:28:45+00:00

[ Upstream commit a40c5d727b8111b5db424a1e43e14a1dcce1e77f ] Reading DPCD registers has side-effects in general. In particular accessing registers outside of the link training register range (0x102-0x106, 0x202-0x207, 0x200c-0x200f, 0x2216) is explicitly forbidden by the DP v2.1 Standard, see 3.6.5.1 DPTX AUX Transaction Handling Mandates 3.6.7.4 128b/132b DP Link Layer LTTPR Link Training Mandates Based on my tests, accessing the DPCD_REV register during the link training of an UHBR TBT DP tunnel sink leads to link training failures. Solve the above by using the DP_LANE0_1_STATUS (0x202) register for the DPCD register access quirk. Cc: Cc: Ville Syrjälä Cc: Jani Nikula Acked-by: Jani Nikula Signed-off-by: Imre Deak Link: https://lore.kernel.org/r/20250605082850.65136-2-imre.deak@intel.com Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

drm/dp_mst: Fix drm RAD print

2025-04-10T12:37:27+00:00

[ Upstream commit 6bbce873a9c97cb12f5455c497be279ac58e707f ] [Why] The RAD of sideband message printed today is incorrect. For RAD stored within MST branch - If MST branch LCT is 1, it's RAD array is untouched and remained as 0. - If MST branch LCT is larger than 1, use nibble to store the up facing port number in cascaded sequence as illustrated below: u8 RAD[0] = (LCT_2_UFP << 4) | LCT_3_UFP RAD[1] = (LCT_4_UFP << 4) | LCT_5_UFP ... In drm_dp_mst_rad_to_str(), it wrongly to use BIT_MASK(4) to fetch the port number of one nibble. [How] Adjust the code by: - RAD array items are valuable only for LCT >= 1. - Use 0xF as the mask to replace BIT_MASK(4) V2: - Document how RAD is constructed (Imre) V3: - Adjust the comment for rad[] so kdoc formats it properly (Lyude) Fixes: 2f015ec6eab6 ("drm/dp_mst: Add sideband down request tracing + selftests") Cc: Imre Deak Cc: Ville Syrjälä Cc: Harry Wentland Cc: Lyude Paul Reviewed-by: Lyude Paul Signed-off-by: Wayne Lin Signed-off-by: Lyude Paul Link: https://patchwork.freedesktop.org/patch/msgid/20250113091100.3314533-2-Wayne.Lin@amd.com Signed-off-by: Sasha Levin

drm/dp_mst: Add a helper to queue a topology probe

2025-04-07T08:06:36+00:00

commit dbaeef363ea54f4c18112874b77503c72ba60fec upstream. A follow up i915 patch will need to reprobe the MST topology after the initial probing, add a helper for this. Cc: Lyude Paul Cc: dri-devel@lists.freedesktop.org Reviewed-by: Lyude Paul Signed-off-by: Imre Deak Link: https://patchwork.freedesktop.org/patch/msgid/20240722165503.2084999-3-imre.deak@intel.com Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman

drm/dp_mst: Factor out function to queue a topology probe work

2025-04-07T08:06:36+00:00

commit e9b36c5be2e7fdef2cc933c1dac50bd81881e9b8 upstream. Factor out a function to queue a work for probing the topology, also used by the next patch. Cc: Lyude Paul Cc: dri-devel@lists.freedesktop.org Reviewed-by: Lyude Paul Signed-off-by: Imre Deak Link: https://patchwork.freedesktop.org/patch/msgid/20240722165503.2084999-2-imre.deak@intel.com Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman