From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53135][LOW] drm/amd/display: Fix NULL deref and buffer over-read in SDP debugfs Date: Fri, 31 Jul 2026 16:53:13 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53135 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: 0 X-AL-KERNEL-Commit: ee9cfcf77a8e8af637396dc00966df5f701e661c List-Id: CVE: CVE-2026-53135 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: drm/amd/display: Fix NULL deref and buffer over-read in SDP debugfs Commit: ee9cfcf77a8e8af637396dc00966df5f701e661c Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee9cfcf77a8e8af637396dc00966df5f701e661c Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53135 Analysis date: Fri, 31 Jul 2026 16:53:13 -0400 ActionableScore: 2 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: YES Summary: A local write to the amdgpu SDP debugfs node can trigger a NULL pointer dereference when the connector has no bound CRTC, and the same path can over-read the caller supplied user buffer, but typical impact is privileged local DoS rather than information disclosure or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53135 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53135 The original announcement does not normally provide a security severity estimate, CVSS assessment, or enough information to determine whether the reported kernel bug represents a practically relevant security issue. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. It combines an autonomous classifier with LLM-assisted technical analysis and a separate ActionableScore mechanism. The purpose of this report is to prioritize Linux kernel CVEs before manual review, identify cases that require prompt investigation, and support automatic closure of issues that are unlikely to have meaningful security impact. Published priority for this report: LOW Manual review required: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-53135 LOW CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H';**CWE-476;CWE-126;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.3';DESCR 'A NULL pointer dereference in dp_sdp_message_debugfs_write() can occur when connector base state or state crtc is NULL while a local process writes to the amdgpu SDP debugfs node. The same path can also read beyond the user supplied buffer because the old code did not clamp the copy length to the write size. This is a local debugfs control path and is not network reachable. For the CVSS the PR:L is used in the paranoid score only for non default deployments where a less privileged local user can write to the affected debugfs node. In typical deployments PR:H is more realistic because debugfs access is restricted to administrators. Impact is mainly denial of service via kernel crash. The user buffer over read may cause limited confidentiality concern only for data reachable from the calling user address space, not a direct kernel memory disclosure or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) SKIP CVE-2026-53135 SKIP No affected files built, so skip this CVE NO - - unknown MAYBE WRITE OOB DANGER SIMPLEFIX KERNEL_PANIC_PLUS_UAF HARDWARE DEBUGFS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown Conservative signals: * Reliable kernel crash / strong DoS: +1. The NULL dereference can crash the kernel when writing to the affected debugfs node while the connector has no bound CRTC. * Requires admin/root/CAP in typical deployments: -2. debugfs access is normally administrator-only or restricted to highly privileged local users. * Hard or state-dependent trigger: -1. The NULL dereference depends on a connector state window such as hot-plug before the next atomic commit. * Rare/non-default exposure path: -1. The vulnerable interface is an AMD display debugfs node, not a default unprivileged syscall or network path. * Floor applied at 0. Paranoid signals: * Local unprivileged trigger: +1. Counted only for non-default deployments where the affected debugfs node is writable by a less privileged local user. * Reliable kernel crash / strong DoS: +1. A successful trigger can cause a kernel crash. * No memory-corruption bonus. The NULL dereference is an invalid pointer dereference, and the copy_from_user issue is a user-buffer over-read, not kernel memory disclosure or a write primitive. * No LPE bonus. The patch does not show UAF, OOB write, object reuse, callback control, refcount abuse, or attacker-controlled overwrite. * No confidentiality bonus in the main score. The over-read reads beyond the caller supplied user buffer, not from kernel memory or another security domain. ## 3. Reachability analysis The bug is local-only and requires writing to the amdgpu SDP debugfs node. In typical deployments this requires administrator-level access because debugfs is restricted or not mounted for unprivileged users. Namespaces normally do not make this broadly reachable unless a container or sandbox is explicitly given access to the host debugfs tree or the specific device debugfs node. There is no network trigger. Realistic exploitation is mainly a local privileged or misconfigured-debugfs kernel crash scenario. Call-site confidence: medium. The vulnerable function and direct dereference/copy path are shown, but broader file permissions and exact debugfs mode are not included in the patch input. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like kernel issue rather than an Important-class vulnerability. The realistic impact is DoS through a NULL pointer dereference. The buffer over-read is not a kernel information leak because copy_from_user reads from the calling process address space. Theoretical escalation is not supported by the patch context, because there is no concrete memory corruption primitive beyond crash-oriented invalid dereference and no attacker-controlled kernel overwrite. ## 5. One-sentence report phrase A local write to the amdgpu SDP debugfs node can trigger a NULL pointer dereference when the connector has no bound CRTC, and the same path can over-read the caller supplied user buffer, but typical impact is privileged local DoS rather than information disclosure or privilege escalation. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED. NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED. Reason: no remote reachability, no strong memory corruption primitive, no plausible LPE path, and typical access requires privileged debugfs write permissions. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: drm/amd/display: Fix NULL deref and buffer over-read in SDP debugfs Commit: ee9cfcf77a8e8af637396dc00966df5f701e661c Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee9cfcf77a8e8af637396dc00966df5f701e661c Commit description: [Why & How] dp_sdp_message_debugfs_write() dereferences connector->base.state->crtc without checking for NULL. A connector can be connected but not bound to any CRTC (e.g. after hot-plug before the next atomic commit), causing a kernel crash when writing to the sdp_message debugfs node. The function also ignores the user-provided size argument and always passes 36 bytes to copy_from_user(), reading past the user buffer when size < 36. Fix both issues by: - Returning -ENODEV when connector->base.state or state->crtc is NULL - Clamping write_size to min(size, sizeof(data)) Fixes: c7ba365 ("drm/amd/display: Generic SDP message access in amdgpu") Assisted-by: Copilot:claude-opus-4.6 Reviewed-by: Alex Hung Signed-off-by: Harry Wentland Signed-off-by: Ray Wu Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher (cherry picked from commit 6ab4c36 ) Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Changed files: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c Diff excerpt: Not included in this email. See the upstream URL for the full patch. Full patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee9cfcf77a8e8af637396dc00966df5f701e661c ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53135 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53135 The original CVE announcement normally does not include a security-level estimate. In particular, it may not contain a CVSS assessment, an impact level, or enough information to determine whether the reported bug is a practically relevant security issue. One purpose of this parallel CVE list is to provide that missing technical and prioritization information. The original goal of the AL-KERNEL project was to prioritize Linux kernel CVE analysis automatically before manual review. The system can also help identify non-security issues that may be suitable for automatic closure. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. The first analysis stage combines an autonomous classifier with additional LLM-based analysis. The autonomous classifier runs locally on a CPU and is based on a backpropagation neural network. Together, these mechanisms produce a technical vulnerability description, identify likely weakness types, estimate CVSS severity, and provide input for ActionableScore. Two CVSS estimates are retained because incomplete kernel vulnerability information often permits more than one defensible interpretation: Conservative CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H The Best / paranoid CVSS score: 5.3 The conservative vector represents a lower-impact interpretation. The Best/paranoid vector intentionally represents a plausible upper-bound interpretation and should not automatically be treated as demonstrated real-world impact. CVSS may also need to be adjusted for a particular Linux deployment, because actual reachability, privileges, enabled kernel configuration, hardware, namespaces, exposed device nodes, and other environmental conditions can differ significantly between systems. A separate ActionableScore mechanism evaluates practical remediation urgency. Its analysis may include reachability, attack prerequisites, subsystem exposure, memory-corruption characteristics, denial-of-service reliability, and possible confidentiality, integrity, or privilege-escalation impact. Conservative ActionableScore: 0 Paranoid ActionableScore: 2 The final base severity is taken directly from the second tab-separated field of the AL-KERNEL classification result. ActionableScore does not replace or independently override that final AL-KERNEL decision, and if ActionableScore adjusted impact level of ALKERNEL, then you would see self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7. For an AL-KERNEL result of MODERATE, this report uses the following additional presentation split: ActionableScore below 5 -> MODERATE REGULAR ActionableScore 5 or more -> MODERATE 7.0 The distinction between MODERATE REGULAR and MODERATE 7.0 makes it possible to identify Moderate issues that should receive manual analysis and fixes before lower-priority MODERATE REGULAR issues. In many cases, MODERATE REGULAR fixes may wait for a later rebase or routine update. There is one override in which MODERATE REGULAR becomes MODERATE 7.0 even when the ActionableScore is below 5. When the AL-KERNEL result contains the KPANIC flag, a MODERATE result is always presented as MODERATE 7.0. The KPANIC flag selected with few regexps without usage of AI at all, so it helps to detect cases when Kernel Crash happens and similar (to filter False-Negative results from the LLM usage). KPANIC indicates that a reliable kernel crash, kernel panic, or similarly serious kernel availability impact was identified by the classification workflow. AL-KERNEL base severity for this report: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW These results are intended to support engineering triage. They are machine-generated estimates, and cases marked for manual review should be validated by a human security engineer before final disposition. For more info read docs linked from here: https://kernelcve.org/ (and you can submit you own patch there to generate such a report for non-existant CVE-id yet). Note that in many cases this AI tool selects higher severity, than real is (means you can expect Importants instead of Moderate 7.0 or Moderates 7.0 instead of regular Moderates). If you see such cases, please use reply email interface to add additional manual analyses info to this particular CVE. And please, please, let me know when you see Lows instead of Importants or Important instead of Low (because particular for such cases I need to tune this AI tool to make it better for this one and next similar). My contact email for such notifications is alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).