Linux-stable-mirror December 2025

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[PATCH 6.1.y v1 0/2] mptcp: Fix conflicts between MPTCP and sockmap

by Jiayuan Chen

Overall, we encountered a warning [1] that can be triggered by running the selftest I provided. sockmap works by replacing sk_data_ready, recvmsg, sendmsg operations and implementing fast socket-level forwarding logic: 1. Users can obtain file descriptors through userspace socket()/accept() interfaces, then call BPF syscall to perform these replacements. 2. Users can also use the bpf_sock_hash_update helper (in sockops programs) to replace handlers when TCP connections enter ESTABLISHED state (BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB/BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB) However, when combined with MPTCP, an issue arises: MPTCP creates subflow sk's and performs TCP handshakes, so the BPF program obtains subflow sk's and may incorrectly replace their sk_prot. We need to reject such operations. In patch 1, we set psock_update_sk_prot to NULL in the subflow's custom sk_prot. Additionally, if the server's listening socket has MPTCP enabled and the client's TCP also uses MPTCP, we should allow the combination of subflow and sockmap. This is because the latest Golang programs have enabled MPTCP for listening sockets by default [2]. For programs already using sockmap, upgrading Golang should not cause sockmap functionality to fail. Patch 2 prevents the panic from occurring. Despite these patches fixing stream corruption, users of sockmap must set GODEBUG=multipathtcp=0 to disable MPTCP until sockmap fully supports it. [1] truncated warning: ------------[ cut here ]------------ BUG: kernel NULL pointer dereference, address: 00000000000004bb PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 0 PID: 400 Comm: test_progs Not tainted 6.1.0+ #16 RIP: 0010:mptcp_stream_accept (./include/linux/list.h:88 net/mptcp/protocol.c:3719) RSP: 0018:ffffc90000ef3cf0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8880089dcc58 RDX: 0000000000000003 RSI: 0000002c000000b0 RDI: 0000000000000000 RBP: ffffc90000ef3d38 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880089dc600 R13: ffff88800b859e00 R14: ffff88800638c680 R15: 0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000004bb CR3: 000000000b8e8006 CR4: 0000000000770ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <TASK> ? apparmor_socket_accept (security/apparmor/lsm.c:966) do_accept (net/socket.c:1856) __sys_accept4 (net/socket.c:1897 net/socket.c:1927) __x64_sys_accept (net/socket.c:1941) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) [2]: https://go-review.googlesource.com/c/go/+/607715 Jiayuan Chen (2): mptcp: disallow MPTCP subflows from sockmap net,mptcp: fix proto fallback detection with BPF net/mptcp/protocol.c | 5 +++-- net/mptcp/subflow.c | 8 ++++++++ 2 files changed, 11 insertions(+), 2 deletions(-) -- 2.43.0

1 month

[PATCH AUTOSEL 6.17-6.12] Revert "drm/amd/display: Move setup_stream_attribute"

by Sasha Levin

From: Alex Deucher <alexander.deucher(a)amd.com> [ Upstream commit 3126c9ccb4373d8758733c6699ba5ab93dbe5c9d ] This reverts commit 2681bf4ae8d24df950138b8c9ea9c271cd62e414. This results in a blank screen on the HDMI port on some systems. Revert for now so as not to regress 6.18, can be addressed in 6.19 once the issue is root caused. Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4652 Cc: Sunpeng.Li(a)amd.com Cc: ivan.lipski(a)amd.com Signed-off-by: Alex Deucher <alexander.deucher(a)amd.com> (cherry picked from commit d0e9de7a81503cdde37fb2d37f1d102f9e0f38fb) Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- LLM Generated explanations, may be completely bogus: Now I have a complete understanding of the issue. Let me summarize my analysis: ## Comprehensive Analysis ### 1. Commit Message Analysis This is a **revert** of commit `2681bf4ae8d24df950138b8c9ea9c271cd62e414` that moved `setup_stream_attribute()` from `link_set_dpms_on()` to individual `enable_stream()` functions. The commit clearly states: - The change "results in a blank screen on the HDMI port on some systems" - Includes a bug report link: https://gitlab.freedesktop.org/drm/amd/-/issues/4652 - Explicitly intended to "not regress 6.18" - Cherry-picked from upstream with maintainer sign-off ### 2. Critical Finding: Buggy Commit Already Backported **The original problematic commit (`7965cb360655`) was already backported to stable trees** (as shown by `[ Upstream commit ... ]` and Sasha Levin's signature). This means **stable users are currently affected by this regression** and need the fix. ### 3. Technical Root Cause The original commit attempted to fix a symclk RCO clock gating issue by moving `setup_stream_attribute()` later in the sequence, after clock ungating in `enable_stream()`. However: - **For DP (DisplayPort)**: This ordering works because DP needs symclk ungated first - **For HDMI/TMDS**: The stream attributes must be set earlier, specifically before VPG power-on and infoframe construction in `link_set_dpms_on()` The code at line 3055 in `dcn20_hwseq.c` shows where the call was moved: ```c link_hwss->setup_stream_attribute(pipe_ctx); ``` This call happens too late for HDMI paths, causing blank screens because the HDMI signal initialization sequence depends on attributes being programmed before the display pipe is fully enabled. ### 4. Code Change Assessment The revert is small and surgical: - **5 files changed** - Removes `link_hwss->setup_stream_attribute()` from 3 hwseq files (dce110, dcn20, dcn401) - Restores the call in `link_dpms.c` at the correct position (after `set_out_mux()`, before VPG power-on) - Removes unused LVDS stub from virtual_stream_encoder.c ### 5. Stable Kernel Rules Compliance | Criteria | Assessment | |----------|------------| | Fixes a real bug affecting users | ✅ Blank HDMI screen - severe user- visible regression | | Obviously correct | ✅ Simple revert to known-working code | | Small and contained | ✅ ~20 lines removed, ~5 lines added | | No new features | ✅ Pure regression fix | | Bug exists in stable | ✅ Original buggy commit was backported | ### 6. Risk Assessment - **Regression risk: LOW** - This reverts to previously known-working behavior that was stable for years - **Trade-off**: The original symclk RCO issue will remain unfixed, but: - RCO issue affects a narrow DP corner case - Blank HDMI affects common consumer hardware - A blank screen is a far worse failure than the clock gating issue - **Testing**: Upstream maintainer sign-off (Alex Deucher) and cherry- picked from mainline ### 7. User Impact - **Severity: CRITICAL** - Complete display failure on HDMI - **Scope: HIGH** - HDMI is ubiquitous; affects multiple hardware generations (dce110, dcn20, dcn401) - **Real users affected**: Bug report confirms actual user impact ### Conclusion This commit is an **ideal stable backport candidate**: 1. The regression-causing commit was already backported to stable trees, so stable users are currently broken 2. It fixes a critical user-visible bug (blank HDMI displays) 3. The fix is a simple, safe revert to known-good code 4. It has proper upstream maintainer approval 5. The risk of the revert causing problems is minimal (returning to proven behavior) The revert is **mandatory** for any stable tree that includes commit `7965cb360655` to restore working HDMI functionality. **YES** drivers/gpu/drm/amd/display/dc/hwss/dce110/dce110_hwseq.c | 1 - drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c | 2 -- drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c | 2 -- drivers/gpu/drm/amd/display/dc/link/link_dpms.c | 3 +++ .../drm/amd/display/dc/virtual/virtual_stream_encoder.c | 7 ------- 5 files changed, 3 insertions(+), 12 deletions(-) diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dce110/dce110_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dce110/dce110_hwseq.c index 537f53811460..39de51cbbde9 100644 --- a/drivers/gpu/drm/amd/display/dc/hwss/dce110/dce110_hwseq.c +++ b/drivers/gpu/drm/amd/display/dc/hwss/dce110/dce110_hwseq.c @@ -671,7 +671,6 @@ void dce110_enable_stream(struct pipe_ctx *pipe_ctx) uint32_t early_control = 0; struct timing_generator *tg = pipe_ctx->stream_res.tg; - link_hwss->setup_stream_attribute(pipe_ctx); link_hwss->setup_stream_encoder(pipe_ctx); dc->hwss.update_info_frame(pipe_ctx); diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c index f7b72b24b750..921023500bec 100644 --- a/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c +++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn20/dcn20_hwseq.c @@ -3052,8 +3052,6 @@ void dcn20_enable_stream(struct pipe_ctx *pipe_ctx) link_enc->transmitter - TRANSMITTER_UNIPHY_A); } - link_hwss->setup_stream_attribute(pipe_ctx); - if (dc->res_pool->dccg->funcs->set_pixel_rate_div) dc->res_pool->dccg->funcs->set_pixel_rate_div( dc->res_pool->dccg, diff --git a/drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c b/drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c index 0fe763704945..b95b98cc2553 100644 --- a/drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c +++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn401/dcn401_hwseq.c @@ -968,8 +968,6 @@ void dcn401_enable_stream(struct pipe_ctx *pipe_ctx) } } - link_hwss->setup_stream_attribute(pipe_ctx); - if (dc->res_pool->dccg->funcs->set_pixel_rate_div) { dc->res_pool->dccg->funcs->set_pixel_rate_div( dc->res_pool->dccg, diff --git a/drivers/gpu/drm/amd/display/dc/link/link_dpms.c b/drivers/gpu/drm/amd/display/dc/link/link_dpms.c index cb80b4599936..8c8682f743d6 100644 --- a/drivers/gpu/drm/amd/display/dc/link/link_dpms.c +++ b/drivers/gpu/drm/amd/display/dc/link/link_dpms.c @@ -2458,6 +2458,7 @@ void link_set_dpms_on( struct link_encoder *link_enc = pipe_ctx->link_res.dio_link_enc; enum otg_out_mux_dest otg_out_dest = OUT_MUX_DIO; struct vpg *vpg = pipe_ctx->stream_res.stream_enc->vpg; + const struct link_hwss *link_hwss = get_link_hwss(link, &pipe_ctx->link_res); bool apply_edp_fast_boot_optimization = pipe_ctx->stream->apply_edp_fast_boot_optimization; @@ -2501,6 +2502,8 @@ void link_set_dpms_on( pipe_ctx->stream_res.tg->funcs->set_out_mux(pipe_ctx->stream_res.tg, otg_out_dest); } + link_hwss->setup_stream_attribute(pipe_ctx); + pipe_ctx->stream->apply_edp_fast_boot_optimization = false; // Enable VPG before building infoframe diff --git a/drivers/gpu/drm/amd/display/dc/virtual/virtual_stream_encoder.c b/drivers/gpu/drm/amd/display/dc/virtual/virtual_stream_encoder.c index 6ffc74fc9dcd..ad088d70e189 100644 --- a/drivers/gpu/drm/amd/display/dc/virtual/virtual_stream_encoder.c +++ b/drivers/gpu/drm/amd/display/dc/virtual/virtual_stream_encoder.c @@ -44,11 +44,6 @@ static void virtual_stream_encoder_dvi_set_stream_attribute( struct dc_crtc_timing *crtc_timing, bool is_dual_link) {} -static void virtual_stream_encoder_lvds_set_stream_attribute( - struct stream_encoder *enc, - struct dc_crtc_timing *crtc_timing) -{} - static void virtual_stream_encoder_set_throttled_vcp_size( struct stream_encoder *enc, struct fixed31_32 avg_time_slots_per_mtp) @@ -120,8 +115,6 @@ static const struct stream_encoder_funcs virtual_str_enc_funcs = { virtual_stream_encoder_hdmi_set_stream_attribute, .dvi_set_stream_attribute = virtual_stream_encoder_dvi_set_stream_attribute, - .lvds_set_stream_attribute = - virtual_stream_encoder_lvds_set_stream_attribute, .set_throttled_vcp_size = virtual_stream_encoder_set_throttled_vcp_size, .update_hdmi_info_packets = -- 2.51.0

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Linux-stable-mirror December 2025