CVE-2021-47256

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And after truncate_error_page clear the mapping\nof this page. end_page_writeback won't call sb_clear_inode_writeback to\nclear inode->i_wb_list. That will trigger BUG_ON in clear_inode!\n\nFix it by checking PageWriteback too to help determine should we skip\nwait_on_page_writeback."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["mm/memory-failure.c"], "versions": [{"version": "0bc1f8b0682caa39f45ce1e0228ebf43acb46111", "lessThan": "d05267fd27a5c4f54e06daefa3035995d765ca0c", "status": "affected", "versionType": "git"}, {"version": "0bc1f8b0682caa39f45ce1e0228ebf43acb46111", "lessThan": "6d210d547adc2218ef8b5bcf23518c5f2f1fd872", "status": "affected", "versionType": "git"}, {"version": "0bc1f8b0682caa39f45ce1e0228ebf43acb46111", "lessThan": "566345aaabac853aa866f53a219c4b02a6beb527", "status": "affected", "versionType": "git"}, {"version": "0bc1f8b0682caa39f45ce1e0228ebf43acb46111", "lessThan": "9e379da727a7a031be9b877cde7b9c34a0fb8306", "status": "affected", "versionType": "git"}, {"version": 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BUG: 0 [#1] SMP\n Modules linked in:\n Process syz-executor.0 (pid: 249, stack limit = 0x00000000a12409d7)\n CPU: 1 PID: 249 Comm: syz-executor.0 Not tainted 4.19.95\n Hardware name: linux,dummy-virt (DT)\n pstate: 80000005 (Nzcv daif -PAN -UAO)\n pc : clear_inode+0x280/0x2a8\n lr : clear_inode+0x280/0x2a8\n Call trace:\n clear_inode+0x280/0x2a8\n ext4_clear_inode+0x38/0xe8\n ext4_free_inode+0x130/0xc68\n ext4_evict_inode+0xb20/0xcb8\n evict+0x1a8/0x3c0\n iput+0x344/0x460\n do_unlinkat+0x260/0x410\n __arm64_sys_unlinkat+0x6c/0xc0\n el0_svc_common+0xdc/0x3b0\n el0_svc_handler+0xf8/0x160\n el0_svc+0x10/0x218\n Kernel panic - not syncing: Fatal exception\n\nA crash dump of this problem show that someone called __munlock_pagevec\nto clear page LRU without lock_page: do_mmap -> mmap_region -> do_munmap\n-> munlock_vma_pages_range -> __munlock_pagevec.\n\nAs a result memory_failure will call identify_page_state without\nwait_on_page_writeback. 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BUG: 0 [#1] SMP\n Modules linked in:\n Process syz-executor.0 (pid: 249, stack limit = 0x00000000a12409d7)\n CPU: 1 PID: 249 Comm: syz-executor.0 Not tainted 4.19.95\n Hardware name: linux,dummy-virt (DT)\n pstate: 80000005 (Nzcv daif -PAN -UAO)\n pc : clear_inode+0x280/0x2a8\n lr : clear_inode+0x280/0x2a8\n Call trace:\n clear_inode+0x280/0x2a8\n ext4_clear_inode+0x38/0xe8\n ext4_free_inode+0x130/0xc68\n ext4_evict_inode+0xb20/0xcb8\n evict+0x1a8/0x3c0\n iput+0x344/0x460\n do_unlinkat+0x260/0x410\n __arm64_sys_unlinkat+0x6c/0xc0\n el0_svc_common+0xdc/0x3b0\n el0_svc_handler+0xf8/0x160\n el0_svc+0x10/0x218\n Kernel panic - not syncing: Fatal exception\n\nA crash dump of this problem show that someone called __munlock_pagevec\nto clear page LRU without lock_page: do_mmap -> mmap_region -> do_munmap\n-> munlock_vma_pages_range -> __munlock_pagevec.\n\nAs a result memory_failure will call identify_page_state without\nwait_on_page_writeback. And after truncate_error_page clear the mapping\nof this page. end_page_writeback won't call sb_clear_inode_writeback to\nclear inode->i_wb_list. That will trigger BUG_ON in clear_inode!\n\nFix it by checking PageWriteback too to help determine should we skip\nwait_on_page_writeback."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: mm/memory-failure: aseg\u00farese de esperar la reescritura de la p\u00e1gina en Memory_failure. Nuestro syzkaller activa el \"BUG_ON(!list_empty(&inode->i_wb_list))\" en clear_inode: kernel BUG en fs /inodo.c:519! Error interno: Oops - BUG: 0 [#1] M\u00f3dulos SMP vinculados en: Proceso syz-executor.0 (pid: 249, l\u00edmite de pila = 0x00000000a12409d7) CPU: 1 PID: 249 Comm: syz-executor.0 No contaminado 4.19. 95 Nombre de hardware: linux,dummy-virt (DT) pstate: 80000005 (Nzcv daif -PAN -UAO) pc: clear_inode+0x280/0x2a8 lr: clear_inode+0x280/0x2a8 Rastreo de llamadas: clear_inode+0x280/0x2a8 ext4_clear_inode+0x38/0xe8 ext4_free_inode+0x130/0xc68 ext4_evict_inode+0xb20/0xcb8 desalojar+0x1a8/0x3c0 iput+0x344/0x460 do_unlinkat+0x260/0x410 __arm64_sys_unlinkat+0x6c/0xc0 el0_svc_common+0xdc /0x3b0 el0_svc_handler+0xf8/0x160 el0_svc+0x10/0x218 P\u00e1nico del kernel: no se sincroniza : Excepci\u00f3n fatal Un volcado de memoria de este problema muestra que alguien llam\u00f3 a __munlock_pagevec para borrar la p\u00e1gina LRU sin lock_page: do_mmap -> mmap_region -> do_munmap -> munlock_vma_pages_range -> __munlock_pagevec. Como resultado, Memory_failure llamar\u00e1 a identify_page_state sin wait_on_page_writeback. Y despu\u00e9s de truncate_error_page, borre el mapeo de esta p\u00e1gina. end_page_writeback no llamar\u00e1 a sb_clear_inode_writeback para borrar inode->i_wb_list. \u00a1Eso activar\u00e1 BUG_ON en clear_inode! Solucionarlo marcando tambi\u00e9n PageWriteback para ayudar a determinar si debemos omitir wait_on_page_writeback."}], "id": "CVE-2021-47256", "lastModified": "2026-06-17T04:17:01.693", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-47256", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2024-09-10T15:39:51.420544Z", "version": "2.0.3"}}]}, "published": "2024-05-21T15:15:14.380", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/28788dc5c70597395b6b451dae4549bbaa8e2c56"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/566345aaabac853aa866f53a219c4b02a6beb527"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6d210d547adc2218ef8b5bcf23518c5f2f1fd872"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/9e379da727a7a031be9b877cde7b9c34a0fb8306"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d05267fd27a5c4f54e06daefa3035995d765ca0c"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/e8675d291ac007e1c636870db880f837a9ea112a"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/28788dc5c70597395b6b451dae4549bbaa8e2c56"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/566345aaabac853aa866f53a219c4b02a6beb527"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6d210d547adc2218ef8b5bcf23518c5f2f1fd872"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/9e379da727a7a031be9b877cde7b9c34a0fb8306"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d05267fd27a5c4f54e06daefa3035995d765ca0c"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/e8675d291ac007e1c636870db880f837a9ea112a"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-noinfo"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: mm/memory-failure: make sure wait for page writeback in memory_failure", "id": "2282554", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2282554"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-567", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nmm/memory-failure: make sure wait for page writeback in memory_failure\nOur syzkaller trigger the \"BUG_ON(!list_empty(&inode->i_wb_list))\" in\nclear_inode:\nkernel BUG at fs/inode.c:519!\nInternal error: Oops - BUG: 0 [#1] SMP\nModules linked in:\nProcess syz-executor.0 (pid: 249, stack limit = 0x00000000a12409d7)\nCPU: 1 PID: 249 Comm: syz-executor.0 Not tainted 4.19.95\nHardware name: linux,dummy-virt (DT)\npstate: 80000005 (Nzcv daif -PAN -UAO)\npc : clear_inode+0x280/0x2a8\nlr : clear_inode+0x280/0x2a8\nCall trace:\nclear_inode+0x280/0x2a8\next4_clear_inode+0x38/0xe8\next4_free_inode+0x130/0xc68\next4_evict_inode+0xb20/0xcb8\nevict+0x1a8/0x3c0\niput+0x344/0x460\ndo_unlinkat+0x260/0x410\n__arm64_sys_unlinkat+0x6c/0xc0\nel0_svc_common+0xdc/0x3b0\nel0_svc_handler+0xf8/0x160\nel0_svc+0x10/0x218\nKernel panic - not syncing: Fatal exception\nA crash dump of this problem show that someone called __munlock_pagevec\nto clear page LRU without lock_page: do_mmap -> mmap_region -> do_munmap\n-> munlock_vma_pages_range -> __munlock_pagevec.\nAs a result memory_failure will call identify_page_state without\nwait_on_page_writeback. And after truncate_error_page clear the mapping\nof this page. end_page_writeback won't call sb_clear_inode_writeback to\nclear inode->i_wb_list. That will trigger BUG_ON in clear_inode!\nFix it by checking PageWriteback too to help determine should we skip\nwait_on_page_writeback.", "A vulnerability was found in the memory_failure function in the Linux kernel's memory management system, where the system may not wait for certain pages to finish writing before performing actions on them, leading to a kernel crash."], "mitigation": {"lang": "en:us", "value": "Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible."}, "name": "CVE-2021-47256", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "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": "2024-05-21T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-47256\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-47256\nhttps://lore.kernel.org/linux-cve-announce/2024052146-CVE-2021-47256-a490@gregkh/T"], "statement": "This vulnerability is rated as a moderate severity because this issue can lead to kernel panics under specific conditions, such as improper memory handling during page writeback, but the exploitation is unlikely in normal scenarios.", "threat_severity": "Moderate"}

{}