CVE-2021-46988

{"id": "CVE-2021-46988", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.5, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 1.8}]}, "published": "2024-02-28T09:15:37.640", "references": [{"url": "https://git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f", "tags": ["Patch"], "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "https://git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de", "tags": ["Patch"], "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "https://git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6", "tags": ["Patch"], "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "https://git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69", "tags": ["Patch"], "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "https://git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c", "tags": ["Patch"], "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "https://git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330", "tags": ["Patch"], "source": "af854a3a-2127-422b-91ae-364da2661108"}, {"url": "https://git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43", "tags": ["Patch"], "source": "af854a3a-2127-422b-91ae-364da2661108"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Primary", "source": "nvd@nist.gov", "description": [{"lang": "en", "value": "CWE-416"}]}], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nuserfaultfd: release page in error path to avoid BUG_ON\n\nConsider the following sequence of events:\n\n1. Userspace issues a UFFD ioctl, which ends up calling into\n shmem_mfill_atomic_pte(). We successfully account the blocks, we\n shmem_alloc_page(), but then the copy_from_user() fails. We return\n -ENOENT. We don't release the page we allocated.\n2. Our caller detects this error code, tries the copy_from_user() after\n dropping the mmap_lock, and retries, calling back into\n shmem_mfill_atomic_pte().\n3. Meanwhile, let's say another process filled up the tmpfs being used.\n4. So shmem_mfill_atomic_pte() fails to account blocks this time, and\n immediately returns - without releasing the page.\n\nThis triggers a BUG_ON in our caller, which asserts that the page\nshould always be consumed, unless -ENOENT is returned.\n\nTo fix this, detect if we have such a \"dangling\" page when accounting\nfails, and if so, release it before returning."}, {"lang": "es", "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: userfaultfd: publicar p\u00e1gina en ruta de error para evitar BUG_ON Considere la siguiente secuencia de eventos: 1. Userspace emite un ioctl UFFD, que termina llamando a shmem_mfill_atomic_pte(). Contamos con \u00e9xito los bloques, usamos shmem_alloc_page(), pero luego copy_from_user() falla. Volvemos -ENOENT. No publicamos la p\u00e1gina que asignamos. 2. Nuestra persona que llama detecta este c\u00f3digo de error, intenta copiar_from_user() despu\u00e9s de descartar mmap_lock y vuelve a intentarlo, volviendo a llamar a shmem_mfill_atomic_pte(). 3. Mientras tanto, digamos que otro proceso llen\u00f3 los tmpfs que se estaban utilizando. 4. Entonces shmem_mfill_atomic_pte() no logra bloquear la cuenta esta vez y regresa inmediatamente, sin liberar la p\u00e1gina. Esto desencadena un BUG_ON en nuestra persona que llama, que afirma que la p\u00e1gina siempre debe consumirse, a menos que se devuelva -ENOENT. Para solucionar este problema, detectar si tenemos esa p\u00e1gina \"colgante\" cuando falla la contabilidad y, en caso afirmativo, liberarla antes de regresar."}], "lastModified": "2024-12-26T15:01:37.110", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "3CEB4F43-643B-4BF2-BC3B-FB797EC75463", "versionEndExcluding": "4.14.233", "versionStartIncluding": "4.11"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "5B6E6817-19A8-4C0A-8807-71DA48CF9191", "versionEndExcluding": "4.19.191", "versionStartIncluding": "4.15"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "2BDC71CF-4451-4D53-93E9-61DE7C4E25B0", "versionEndExcluding": "5.4.120", "versionStartIncluding": "4.20"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "2BB4E5E8-4AAD-475A-A1B9-F287254C7D72", "versionEndExcluding": "5.10.38", "versionStartIncluding": "5.5"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "83B53E9A-F426-4C03-9A5F-A931FF79827E", "versionEndExcluding": "5.11.22", "versionStartIncluding": "5.11"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "0274929A-B36C-4F4C-AB22-30A0DD6B995B", "versionEndExcluding": "5.12.5", "versionStartIncluding": "5.12"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "0CBAD0FC-C281-4666-AB2F-F8E6E1165DF7"}], "operator": "OR"}]}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}