{"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":"2026-05-11T22:13:02.448Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-05-11T22:13:02.448Z"},"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"}}],"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":"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":"5.15.203","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":"5.15.203"},{"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/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"}}}}