{"api_version":"1","generated_at":"2026-10-01T12:49:23+00:00","cve":"CVE-2026-89956","urls":{"html":"https://cve.report/CVE-2026-89956","api":"https://cve.report/api/cve/CVE-2026-89956.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-89956","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-89956"},"summary":{"title":"s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ns390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects\n\nIn order to traverse or add/remove ap_matrix_mdev objects in the\nmatrix_dev->mdev_list, the matrix_dev->guests_lock mutex must be held.\nThere are two functions that access the list without holding the mutex:\n\nvfio_ap_mdev_probe function\n~~~~~~~~~~~~~~~~~~~~~~~~~~~\nThe vfio_ap_mdev_probe function uses the matrix_dev->mdevs_lock\nmutex to guard the add of a newly created ap_matrix_mdev object to the\nmatrix_dev->mdev_list. This mutex does not protect list access; its purpose\nis to guard against concurrent access to fields contained in an\nap_matrix_mdev object. This could lead to kernel memory corruption or\nuse-after-free if another mdev is created or removed concurrently.\n\nThe adding of an ap_matrix_mdev object to matrix_dev->mdev_list\nis now guarded by the matrix_dev->guests_lock which is the correct\nway to protect against concurrent mdev_list access.\n\nAlso removed the following two lines of code because the matrix_mdev is\nallocated via vfio_alloc_device macro which uses kzalloc, so req_trigger\nand cfg_chg_trigger are already zero-initialised when the struct is\nallocated before the call to vfio_register_emulated_iommu_dev. This\nprevents a window whereby these triggers are set to NULL after\nthe device is exposed to userspace.\n\nmatrix_mdev->req_trigger = NULL;\nmatrix_mdev->cfg_chg_trigger = NULL;\n\nvfio_ap_mdev_for_queue function\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\nThe status_show function that supports display of the status attribute of\nthe devices in /sys/bus/ap/devices calls the vfio_ap_mdev_for_queue\nfunction which iterates the matrix_dev->mdev_list to find the object\nrepresenting the queue device whose status is to be displayed. In order to\ntraverse this list, the matrix_dev->guests_lock mutex must be held.\n\nTo fix this, the guests_lock mutex is taken prior to taking the\nmatrix_dev->mdevs_lock mutex in the status_show function. It is taken\nthere rather than the vfio_ap_mdev_for_queue function - where it is\nneeded - because it must be taken prior to the mdevs_lock mutex in order to\nadhere to the proper locking order and prevent a lockdep splat; also\nbecause the mdevs_lock is needed there to access fields within\nthe matrix_mdev object in that function.\n\nSee the vfio-ap-locking.rst in the linux kernel tree.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-16 11:17:05","updated_at":"2026-09-16 11:17:05"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/0fd74477d05743d4cd9b25a3b667daa278d53b93","name":"https://git.kernel.org/stable/c/0fd74477d05743d4cd9b25a3b667daa278d53b93","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/647916988272fe5ecb4bb30cd02b51af9960618a","name":"https://git.kernel.org/stable/c/647916988272fe5ecb4bb30cd02b51af9960618a","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/7fa61c29850d05e40ca9ed41bfdf57673023f581","name":"https://git.kernel.org/stable/c/7fa61c29850d05e40ca9ed41bfdf57673023f581","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89956","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89956","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 2c1ee8983aa377fef4f725162f4f3aa5f9575d4a 647916988272fe5ecb4bb30cd02b51af9960618a git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 2c1ee8983aa377fef4f725162f4f3aa5f9575d4a 0fd74477d05743d4cd9b25a3b667daa278d53b93 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 2c1ee8983aa377fef4f725162f4f3aa5f9575d4a 7fa61c29850d05e40ca9ed41bfdf57673023f581 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.0","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.0 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.51 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.5 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["drivers/s390/crypto/vfio_ap_ops.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"647916988272fe5ecb4bb30cd02b51af9960618a","status":"affected","version":"2c1ee8983aa377fef4f725162f4f3aa5f9575d4a","versionType":"git"},{"lessThan":"0fd74477d05743d4cd9b25a3b667daa278d53b93","status":"affected","version":"2c1ee8983aa377fef4f725162f4f3aa5f9575d4a","versionType":"git"},{"lessThan":"7fa61c29850d05e40ca9ed41bfdf57673023f581","status":"affected","version":"2c1ee8983aa377fef4f725162f4f3aa5f9575d4a","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["drivers/s390/crypto/vfio_ap_ops.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.0"},{"lessThan":"6.0","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.51","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.5","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.51","versionStartIncluding":"6.0","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.5","versionStartIncluding":"6.0","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc1","versionStartIncluding":"6.0","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ns390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects\n\nIn order to traverse or add/remove ap_matrix_mdev objects in the\nmatrix_dev->mdev_list, the matrix_dev->guests_lock mutex must be held.\nThere are two functions that access the list without holding the mutex:\n\nvfio_ap_mdev_probe function\n~~~~~~~~~~~~~~~~~~~~~~~~~~~\nThe vfio_ap_mdev_probe function uses the matrix_dev->mdevs_lock\nmutex to guard the add of a newly created ap_matrix_mdev object to the\nmatrix_dev->mdev_list. This mutex does not protect list access; its purpose\nis to guard against concurrent access to fields contained in an\nap_matrix_mdev object. This could lead to kernel memory corruption or\nuse-after-free if another mdev is created or removed concurrently.\n\nThe adding of an ap_matrix_mdev object to matrix_dev->mdev_list\nis now guarded by the matrix_dev->guests_lock which is the correct\nway to protect against concurrent mdev_list access.\n\nAlso removed the following two lines of code because the matrix_mdev is\nallocated via vfio_alloc_device macro which uses kzalloc, so req_trigger\nand cfg_chg_trigger are already zero-initialised when the struct is\nallocated before the call to vfio_register_emulated_iommu_dev. This\nprevents a window whereby these triggers are set to NULL after\nthe device is exposed to userspace.\n\nmatrix_mdev->req_trigger = NULL;\nmatrix_mdev->cfg_chg_trigger = NULL;\n\nvfio_ap_mdev_for_queue function\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\nThe status_show function that supports display of the status attribute of\nthe devices in /sys/bus/ap/devices calls the vfio_ap_mdev_for_queue\nfunction which iterates the matrix_dev->mdev_list to find the object\nrepresenting the queue device whose status is to be displayed. In order to\ntraverse this list, the matrix_dev->guests_lock mutex must be held.\n\nTo fix this, the guests_lock mutex is taken prior to taking the\nmatrix_dev->mdevs_lock mutex in the status_show function. It is taken\nthere rather than the vfio_ap_mdev_for_queue function - where it is\nneeded - because it must be taken prior to the mdevs_lock mutex in order to\nadhere to the proper locking order and prevent a lockdep splat; also\nbecause the mdevs_lock is needed there to access fields within\nthe matrix_mdev object in that function.\n\nSee the vfio-ap-locking.rst in the linux kernel tree."}],"providerMetadata":{"dateUpdated":"2026-09-16T10:32:39.847Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/647916988272fe5ecb4bb30cd02b51af9960618a"},{"url":"https://git.kernel.org/stable/c/0fd74477d05743d4cd9b25a3b667daa278d53b93"},{"url":"https://git.kernel.org/stable/c/7fa61c29850d05e40ca9ed41bfdf57673023f581"}],"title":"s390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-89956","datePublished":"2026-09-16T10:32:39.847Z","dateReserved":"2026-09-11T19:38:34.778Z","dateUpdated":"2026-09-16T10:32:39.847Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-16 11:17:05","lastModifiedDate":"2026-09-16 11:17:05","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"89956","Ordinal":"1","Title":"s390/vfio-ap: Fix missing lock required to access list of ap_mat","CVE":"CVE-2026-89956","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"89956","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\ns390/vfio-ap: Fix missing lock required to access list of ap_matrix_mdev objects\n\nIn order to traverse or add/remove ap_matrix_mdev objects in the\nmatrix_dev->mdev_list, the matrix_dev->guests_lock mutex must be held.\nThere are two functions that access the list without holding the mutex:\n\nvfio_ap_mdev_probe function\n~~~~~~~~~~~~~~~~~~~~~~~~~~~\nThe vfio_ap_mdev_probe function uses the matrix_dev->mdevs_lock\nmutex to guard the add of a newly created ap_matrix_mdev object to the\nmatrix_dev->mdev_list. This mutex does not protect list access; its purpose\nis to guard against concurrent access to fields contained in an\nap_matrix_mdev object. This could lead to kernel memory corruption or\nuse-after-free if another mdev is created or removed concurrently.\n\nThe adding of an ap_matrix_mdev object to matrix_dev->mdev_list\nis now guarded by the matrix_dev->guests_lock which is the correct\nway to protect against concurrent mdev_list access.\n\nAlso removed the following two lines of code because the matrix_mdev is\nallocated via vfio_alloc_device macro which uses kzalloc, so req_trigger\nand cfg_chg_trigger are already zero-initialised when the struct is\nallocated before the call to vfio_register_emulated_iommu_dev. This\nprevents a window whereby these triggers are set to NULL after\nthe device is exposed to userspace.\n\nmatrix_mdev->req_trigger = NULL;\nmatrix_mdev->cfg_chg_trigger = NULL;\n\nvfio_ap_mdev_for_queue function\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\nThe status_show function that supports display of the status attribute of\nthe devices in /sys/bus/ap/devices calls the vfio_ap_mdev_for_queue\nfunction which iterates the matrix_dev->mdev_list to find the object\nrepresenting the queue device whose status is to be displayed. In order to\ntraverse this list, the matrix_dev->guests_lock mutex must be held.\n\nTo fix this, the guests_lock mutex is taken prior to taking the\nmatrix_dev->mdevs_lock mutex in the status_show function. It is taken\nthere rather than the vfio_ap_mdev_for_queue function - where it is\nneeded - because it must be taken prior to the mdevs_lock mutex in order to\nadhere to the proper locking order and prevent a lockdep splat; also\nbecause the mdevs_lock is needed there to access fields within\nthe matrix_mdev object in that function.\n\nSee the vfio-ap-locking.rst in the linux kernel tree.","Type":"Description","Title":"s390/vfio-ap: Fix missing lock required to access list of ap_mat"}]}}}