CVE-2026-31656

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-31656", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-03-09T15:48:24.129Z", "datePublished": "2026-04-24T14:45:07.738Z", "dateUpdated": "2026-10-19T18:56:01.711Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:24:09.663Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat\n\nA use-after-free / refcount underflow is possible when the heartbeat\nworker and intel_engine_park_heartbeat() race to release the same\nengine->heartbeat.systole request.\n\nThe heartbeat worker reads engine->heartbeat.systole and calls\ni915_request_put() on it when the request is complete, but clears\nthe pointer in a separate, non-atomic step. Concurrently, a request\nretirement on another CPU can drop the engine wakeref to zero, triggering\n__engine_park() -> intel_engine_park_heartbeat(). If the heartbeat\ntimer is pending at that point, cancel_delayed_work() returns true and\nintel_engine_park_heartbeat() reads the stale non-NULL systole pointer\nand calls i915_request_put() on it again, causing a refcount underflow:\n\n```\n<4> [487.221889] Workqueue: i915-unordered engine_retire [i915]\n<4> [487.222640] RIP: 0010:refcount_warn_saturate+0x68/0xb0\n...\n<4> [487.222707] Call Trace:\n<4> [487.222711] <TASK>\n<4> [487.222716] intel_engine_park_heartbeat.part.0+0x6f/0x80 [i915]\n<4> [487.223115] intel_engine_park_heartbeat+0x25/0x40 [i915]\n<4> [487.223566] __engine_park+0xb9/0x650 [i915]\n<4> [487.223973] ____intel_wakeref_put_last+0x2e/0xb0 [i915]\n<4> [487.224408] __intel_wakeref_put_last+0x72/0x90 [i915]\n<4> [487.224797] intel_context_exit_engine+0x7c/0x80 [i915]\n<4> [487.225238] intel_context_exit+0xf1/0x1b0 [i915]\n<4> [487.225695] i915_request_retire.part.0+0x1b9/0x530 [i915]\n<4> [487.226178] i915_request_retire+0x1c/0x40 [i915]\n<4> [487.226625] engine_retire+0x122/0x180 [i915]\n<4> [487.227037] process_one_work+0x239/0x760\n<4> [487.227060] worker_thread+0x200/0x3f0\n<4> [487.227068] ? __pfx_worker_thread+0x10/0x10\n<4> [487.227075] kthread+0x10d/0x150\n<4> [487.227083] ? __pfx_kthread+0x10/0x10\n<4> [487.227092] ret_from_fork+0x3d4/0x480\n<4> [487.227099] ? __pfx_kthread+0x10/0x10\n<4> [487.227107] ret_from_fork_asm+0x1a/0x30\n<4> [487.227141] </TASK>\n```\n\nFix this by replacing the non-atomic pointer read + separate clear with\nxchg() in both racing paths. xchg() is a single indivisible hardware\ninstruction that atomically reads the old pointer and writes NULL. This\nguarantees only one of the two concurrent callers obtains the non-NULL\npointer and performs the put, the other gets NULL and skips it.\n\n(cherry picked from commit 13238dc0ee4f9ab8dafa2cca7295736191ae2f42)"}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:L - The vulnerable path is reached locally through i915 DRM render ioctls such as execbuffer submission, not through network or adjacent protocols.\nAC:L - Although the bug is a race, an attacker with render access can repeatedly drive GPU request submission, heartbeat creation, completion, retirement, and engine parking to trigger it.\nPR:L - The relevant ioctl is DRM_RENDER_ALLOW and does not require CAP_SYS_ADMIN or DRM master, but the attacker needs local access to an i915 render device as an unprivileged render client.\nUI:N - No victim action is required once the attacker can issue DRM ioctls and submit GPU work.\nS:U - The impact remains within the kernel/driver security authority; this is not a VM escape or cross-scope boundary bypass.\nC:H - The stale i915_request pointer can become a use-after-free on a reused request object, and per the required kernel scoring guidance UAFs are treated as enabling high confidentiality impact.\nI:H - The double put/refcount underflow can corrupt request/fence lifetime state and create a UAF condition, which is defensibly exploitable for arbitrary kernel memory manipulation.\nA:H - The observed failure reaches refcount_warn_saturate from the engine park path and can produce a kernel warning/oops or crash; repeated triggering can deny service."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c"], "versions": [{"version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "82034799c6c14b3104668878c3f3e5786f777126", "status": "affected", "versionType": "git"}, {"version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "70d3e622b10092fc483e28e57b4e8c49d9cc7f68", "status": "affected", "versionType": "git"}, {"version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "8ce44d28a84fd5e053a88b04872a89d95c0779d4", "status": "affected", "versionType": "git"}, {"version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "ca3f48c3567dd49efdc55b80029ae74659c682ee", "status": "affected", "versionType": "git"}, {"version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "a00e92bf6583d019a4fb2c2df7007e6c9b269ce7", "status": "affected", "versionType": "git"}, {"version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "2af8b200cae3fdd0e917ecc2753b28bb40c876c1", "status": "affected", "versionType": "git"}, {"version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "455d98ed527fc94eed90406f90ab2391464ca657", "status": "affected", "versionType": "git"}, {"version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "4c71fd099513bfa8acab529b626e1f0097b76061", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c"], "versions": [{"version": "5.5", "status": "affected"}, {"version": "0", "lessThan": "5.5", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.258", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.203", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.169", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.135", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.82", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.23", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19.13", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5", "versionEndExcluding": "5.10.258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5", "versionEndExcluding": "5.15.203"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5", "versionEndExcluding": "6.1.169"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5", "versionEndExcluding": "6.6.135"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5", "versionEndExcluding": "6.12.82"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5", "versionEndExcluding": "6.18.23"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5", "versionEndExcluding": "6.19.13"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.5", "versionEndExcluding": "7.0"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/82034799c6c14b3104668878c3f3e5786f777126"}, {"url": "https://git.kernel.org/stable/c/70d3e622b10092fc483e28e57b4e8c49d9cc7f68"}, {"url": "https://git.kernel.org/stable/c/8ce44d28a84fd5e053a88b04872a89d95c0779d4"}, {"url": "https://git.kernel.org/stable/c/ca3f48c3567dd49efdc55b80029ae74659c682ee"}, {"url": "https://git.kernel.org/stable/c/a00e92bf6583d019a4fb2c2df7007e6c9b269ce7"}, {"url": "https://git.kernel.org/stable/c/2af8b200cae3fdd0e917ecc2753b28bb40c876c1"}, {"url": "https://git.kernel.org/stable/c/455d98ed527fc94eed90406f90ab2391464ca657"}, {"url": "https://git.kernel.org/stable/c/4c71fd099513bfa8acab529b626e1f0097b76061"}], "title": "drm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-31656", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-10-16T15:11:35.318678Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-362", "description": "CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization 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{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-31656", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-10-16T15:11:35.318678Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T15:11:35.987Z"}}], "cna": {"title": "drm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat", "metrics": [{"cvssV3_1": {"version": "3.1", "baseScore": 7.8, "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}, "scenarios": [{"lang": "en", "value": "AV:L - The vulnerable path is reached locally through i915 DRM render ioctls such as execbuffer submission, not through network or adjacent protocols.\nAC:L - Although the bug is a race, an attacker with render access can repeatedly drive GPU request submission, heartbeat creation, completion, retirement, and engine parking to trigger it.\nPR:L - The relevant ioctl is DRM_RENDER_ALLOW and does not require CAP_SYS_ADMIN or DRM master, but the attacker needs local access to an i915 render device as an unprivileged render client.\nUI:N - No victim action is required once the attacker can issue DRM ioctls and submit GPU work.\nS:U - The impact remains within the kernel/driver security authority; this is not a VM escape or cross-scope boundary bypass.\nC:H - The stale i915_request pointer can become a use-after-free on a reused request object, and per the required kernel scoring guidance UAFs are treated as enabling high confidentiality impact.\nI:H - The double put/refcount underflow can corrupt request/fence lifetime state and create a UAF condition, which is defensibly exploitable for arbitrary kernel memory manipulation.\nA:H - The observed failure reaches refcount_warn_saturate from the engine park path and can produce a kernel warning/oops or crash; repeated triggering can deny service."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "82034799c6c14b3104668878c3f3e5786f777126", "versionType": "git"}, {"status": "affected", "version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "70d3e622b10092fc483e28e57b4e8c49d9cc7f68", "versionType": "git"}, {"status": "affected", "version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "8ce44d28a84fd5e053a88b04872a89d95c0779d4", "versionType": "git"}, {"status": "affected", "version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "ca3f48c3567dd49efdc55b80029ae74659c682ee", "versionType": "git"}, {"status": "affected", "version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "a00e92bf6583d019a4fb2c2df7007e6c9b269ce7", "versionType": "git"}, {"status": "affected", "version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "2af8b200cae3fdd0e917ecc2753b28bb40c876c1", "versionType": "git"}, {"status": "affected", "version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "455d98ed527fc94eed90406f90ab2391464ca657", "versionType": "git"}, {"status": "affected", "version": "058179e72e0956a2dfe4927db6cbe5fbfb2406aa", "lessThan": "4c71fd099513bfa8acab529b626e1f0097b76061", "versionType": "git"}], "programFiles": ["drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "5.5"}, {"status": "unaffected", "version": "0", "lessThan": "5.5", "versionType": "semver"}, {"status": "unaffected", "version": "5.10.258", "versionType": "semver", "lessThanOrEqual": "5.10.*"}, {"status": "unaffected", "version": "5.15.203", "versionType": "semver", "lessThanOrEqual": "5.15.*"}, {"status": "unaffected", "version": "6.1.169", "versionType": "semver", "lessThanOrEqual": "6.1.*"}, {"status": "unaffected", "version": "6.6.135", "versionType": "semver", "lessThanOrEqual": "6.6.*"}, {"status": "unaffected", "version": "6.12.82", "versionType": "semver", "lessThanOrEqual": "6.12.*"}, {"status": "unaffected", "version": "6.18.23", "versionType": "semver", "lessThanOrEqual": "6.18.*"}, {"status": "unaffected", "version": "6.19.13", "versionType": "semver", "lessThanOrEqual": "6.19.*"}, {"status": "unaffected", "version": "7.0", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["drivers/gpu/drm/i915/gt/intel_engine_heartbeat.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/82034799c6c14b3104668878c3f3e5786f777126"}, {"url": "https://git.kernel.org/stable/c/70d3e622b10092fc483e28e57b4e8c49d9cc7f68"}, {"url": "https://git.kernel.org/stable/c/8ce44d28a84fd5e053a88b04872a89d95c0779d4"}, {"url": "https://git.kernel.org/stable/c/ca3f48c3567dd49efdc55b80029ae74659c682ee"}, {"url": "https://git.kernel.org/stable/c/a00e92bf6583d019a4fb2c2df7007e6c9b269ce7"}, {"url": "https://git.kernel.org/stable/c/2af8b200cae3fdd0e917ecc2753b28bb40c876c1"}, {"url": "https://git.kernel.org/stable/c/455d98ed527fc94eed90406f90ab2391464ca657"}, {"url": "https://git.kernel.org/stable/c/4c71fd099513bfa8acab529b626e1f0097b76061"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat\n\nA use-after-free / refcount underflow is possible when the heartbeat\nworker and intel_engine_park_heartbeat() race to release the same\nengine->heartbeat.systole request.\n\nThe heartbeat worker reads engine->heartbeat.systole and calls\ni915_request_put() on it when the request is complete, but clears\nthe pointer in a separate, non-atomic step. Concurrently, a request\nretirement on another CPU can drop the engine wakeref to zero, triggering\n__engine_park() -> intel_engine_park_heartbeat(). If the heartbeat\ntimer is pending at that point, cancel_delayed_work() returns true and\nintel_engine_park_heartbeat() reads the stale non-NULL systole pointer\nand calls i915_request_put() on it again, causing a refcount underflow:\n\n```\n<4> [487.221889] Workqueue: i915-unordered engine_retire [i915]\n<4> [487.222640] RIP: 0010:refcount_warn_saturate+0x68/0xb0\n...\n<4> [487.222707] Call Trace:\n<4> [487.222711] <TASK>\n<4> [487.222716] intel_engine_park_heartbeat.part.0+0x6f/0x80 [i915]\n<4> [487.223115] intel_engine_park_heartbeat+0x25/0x40 [i915]\n<4> [487.223566] __engine_park+0xb9/0x650 [i915]\n<4> [487.223973] ____intel_wakeref_put_last+0x2e/0xb0 [i915]\n<4> [487.224408] __intel_wakeref_put_last+0x72/0x90 [i915]\n<4> [487.224797] intel_context_exit_engine+0x7c/0x80 [i915]\n<4> [487.225238] intel_context_exit+0xf1/0x1b0 [i915]\n<4> [487.225695] i915_request_retire.part.0+0x1b9/0x530 [i915]\n<4> [487.226178] i915_request_retire+0x1c/0x40 [i915]\n<4> [487.226625] engine_retire+0x122/0x180 [i915]\n<4> [487.227037] process_one_work+0x239/0x760\n<4> [487.227060] worker_thread+0x200/0x3f0\n<4> [487.227068] ? __pfx_worker_thread+0x10/0x10\n<4> [487.227075] kthread+0x10d/0x150\n<4> [487.227083] ? __pfx_kthread+0x10/0x10\n<4> [487.227092] ret_from_fork+0x3d4/0x480\n<4> [487.227099] ? __pfx_kthread+0x10/0x10\n<4> [487.227107] ret_from_fork_asm+0x1a/0x30\n<4> [487.227141] </TASK>\n```\n\nFix this by replacing the non-atomic pointer read + separate clear with\nxchg() in both racing paths. xchg() is a single indivisible hardware\ninstruction that atomically reads the old pointer and writes NULL. This\nguarantees only one of the two concurrent callers obtains the non-NULL\npointer and performs the put, the other gets NULL and skips it.\n\n(cherry picked from commit 13238dc0ee4f9ab8dafa2cca7295736191ae2f42)"}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.10.258", "versionStartIncluding": "5.5"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.15.203", "versionStartIncluding": "5.5"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.1.169", "versionStartIncluding": "5.5"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.6.135", "versionStartIncluding": "5.5"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.12.82", "versionStartIncluding": "5.5"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.18.23", "versionStartIncluding": "5.5"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.19.13", "versionStartIncluding": "5.5"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "7.0", "versionStartIncluding": "5.5"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:24:09.663Z"}}}, "cveMetadata": {"cveId": "CVE-2026-31656", "state": "PUBLISHED", "dateUpdated": "2026-10-19T18:56:01.711Z", "dateReserved": "2026-03-09T15:48:24.129Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2026-04-24T14:45:07.738Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

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"cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat\n\nA use-after-free / refcount underflow is possible when the heartbeat\nworker and intel_engine_park_heartbeat() race to release the same\nengine->heartbeat.systole request.\n\nThe heartbeat worker reads engine->heartbeat.systole and calls\ni915_request_put() on it when the request is complete, but clears\nthe pointer in a separate, non-atomic step. Concurrently, a request\nretirement on another CPU can drop the engine wakeref to zero, triggering\n__engine_park() -> intel_engine_park_heartbeat(). If the heartbeat\ntimer is pending at that point, cancel_delayed_work() returns true and\nintel_engine_park_heartbeat() reads the stale non-NULL systole pointer\nand calls i915_request_put() on it again, causing a refcount underflow:\n\n```\n<4> [487.221889] Workqueue: i915-unordered engine_retire [i915]\n<4> [487.222640] RIP: 0010:refcount_warn_saturate+0x68/0xb0\n...\n<4> [487.222707] Call Trace:\n<4> [487.222711] <TASK>\n<4> [487.222716] intel_engine_park_heartbeat.part.0+0x6f/0x80 [i915]\n<4> [487.223115] intel_engine_park_heartbeat+0x25/0x40 [i915]\n<4> [487.223566] __engine_park+0xb9/0x650 [i915]\n<4> [487.223973] ____intel_wakeref_put_last+0x2e/0xb0 [i915]\n<4> [487.224408] __intel_wakeref_put_last+0x72/0x90 [i915]\n<4> [487.224797] intel_context_exit_engine+0x7c/0x80 [i915]\n<4> [487.225238] intel_context_exit+0xf1/0x1b0 [i915]\n<4> [487.225695] i915_request_retire.part.0+0x1b9/0x530 [i915]\n<4> [487.226178] i915_request_retire+0x1c/0x40 [i915]\n<4> [487.226625] engine_retire+0x122/0x180 [i915]\n<4> [487.227037] process_one_work+0x239/0x760\n<4> [487.227060] worker_thread+0x200/0x3f0\n<4> [487.227068] ? __pfx_worker_thread+0x10/0x10\n<4> [487.227075] kthread+0x10d/0x150\n<4> [487.227083] ? __pfx_kthread+0x10/0x10\n<4> [487.227092] ret_from_fork+0x3d4/0x480\n<4> [487.227099] ? __pfx_kthread+0x10/0x10\n<4> [487.227107] ret_from_fork_asm+0x1a/0x30\n<4> [487.227141] </TASK>\n```\n\nFix this by replacing the non-atomic pointer read + separate clear with\nxchg() in both racing paths. xchg() is a single indivisible hardware\ninstruction that atomically reads the old pointer and writes NULL. This\nguarantees only one of the two concurrent callers obtains the non-NULL\npointer and performs the put, the other gets NULL and skips it.\n\n(cherry picked from commit 13238dc0ee4f9ab8dafa2cca7295736191ae2f42)"}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta: drm/i915/gt: corregir desbordamiento negativo de contador de referencias en intel_engine_park_heartbeat Un uso despu\u00e9s de liberaci\u00f3n / desbordamiento negativo de contador de referencias es posible cuando el worker de heartbeat y intel_engine_park_heartbeat() compiten para liberar la misma solicitud engine -> heartbeat.systole. El worker de heartbeat lee engine -> heartbeat.systole y llama a i915_request_put() sobre ella cuando la solicitud est\u00e1 completa, pero borra el puntero en un paso separado y no at\u00f3mico. Simult\u00e1neamente, una retirada de solicitud en otra CPU puede reducir el wakeref del motor a cero, lo que activa __engine_park() -> intel_engine_park_heartbeat(). Si el temporizador de heartbeat est\u00e1 pendiente en ese momento, cancel_delayed_work() devuelve verdadero e intel_engine_park_heartbeat() lee el puntero systole obsoleto no nulo y llama a i915_request_put() sobre \u00e9l de nuevo, causando un desbordamiento negativo de contador de referencias: \u201d\u201d\u201c\nmenor que 4> [487.221889] Workqueue: i915-unordered engine_retire [i915]\nmenor que 4> [487.222640] RIP: 0010:refcount_warn_saturate+0x68/0xb0\n...\nmenor que 4> [487.222707] Call Trace:\nmenor que 4> [487.222711] [TASK]\nmenor que 4> [487.222716] intel_engine_park_heartbeat.part.0+0x6f/0x80 [i915]\nmenor que 4> [487.223115] intel_engine_park_heartbeat+0x25/0x40 [i915]\nmenor que 4> [487.223566] __engine_park+0xb9/0x650 [i915]\nmenor que 4> [487.223973] ____intel_wakeref_put_last+0x2e/0xb0 [i915]\nmenor que 4> [487.224408] __intel_wakeref_put_last+0x72/0x90 [i915]\nmenor que 4> [487.224797] intel_context_exit_engine+0x7c/0x80 [i915]\nmenor que 4> [487.225238] intel_context_exit+0xf1/0x1b0 [i915]\nmenor que 4> [487.225695] i915_request_retire.part.0+0x1b9/0x530 [i915]\nmenor que 4> [487.226178] i915_request_retire+0x1c/0x40 [i915]\nmenor que 4> [487.226625] engine_retire+0x122/0x180 [i915]\nmenor que 4> [487.227037] process_one_work+0x239/0x760\nmenor que 4> [487.227060] worker_thread+0x200/0x3f0\nmenor que 4> [487.227068] ? __pfx_worker_thread+0x10/0x10\nmenor que 4> [487.227075] kthread+0x10d/0x150\nmenor que 4> [487.227083] ? __pfx_kthread+0x10/0x10\nmenor que 4> [487.227092] ret_from_fork+0x3d4/0x480\nmenor que 4> [487.227099] ? __pfx_kthread+0x10/0x10\nmenor que 4> [487.227107] ret_from_fork_asm+0x1a/0x30\nmenor que 4> [487.227141] [/TASK]\n\u201d\u201d\u201d Solucione esto reemplazando la lectura de puntero no at\u00f3mica + borrado separado con xchg() en ambas rutas de carrera. xchg() es una \u00fanica instrucci\u00f3n de hardware indivisible que lee at\u00f3micamente el puntero antiguo y escribe NULL. Esto garantiza que solo uno de los dos llamadores concurrentes obtiene el puntero no nulo y realiza el \u2019put\u2019, el otro obtiene NULL y lo omite. (seleccionado de la confirmaci\u00f3n 13238dc0ee4f9ab8dafa2cca7295736191ae2f42)"}], "id": "CVE-2026-31656", "lastModified": "2026-11-11T23:10:00.263", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-31656", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-10-16T15:11:35.318678Z", "version": "2.0.3"}}]}, "published": "2026-04-24T15:16:45.097", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/2af8b200cae3fdd0e917ecc2753b28bb40c876c1"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/455d98ed527fc94eed90406f90ab2391464ca657"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/4c71fd099513bfa8acab529b626e1f0097b76061"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/70d3e622b10092fc483e28e57b4e8c49d9cc7f68"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/82034799c6c14b3104668878c3f3e5786f777126"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/8ce44d28a84fd5e053a88b04872a89d95c0779d4"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a00e92bf6583d019a4fb2c2df7007e6c9b269ce7"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ca3f48c3567dd49efdc55b80029ae74659c682ee"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-191"}], "source": "nvd@nist.gov", "type": "Primary"}, {"description": [{"lang": "en", "value": "CWE-362"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "kernel: drm/i915/gt: fix refcount underflow in intel_engine_park_heartbeat", "id": "2461525", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2461525"}, "csaw": false, "cwe": "CWE-911", "details": ["A flaw was found in the Linux kernel's i915 graphics driver. A race condition exists between the heartbeat worker and `intel_engine_park_heartbeat()` functions when releasing an engine request. This can lead to a reference count (refcount) underflow, resulting in a use-after-free vulnerability. A local attacker could potentially exploit this to cause a denial of service."], "name": "CVE-2026-31656", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-04-24T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-31656\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31656\nhttps://lore.kernel.org/linux-cve-announce/2026042402-CVE-2026-31656-050b@gregkh/T"]}

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