CVE-2021-46988

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2021-46988", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-02-27T18:42:55.948Z", "datePublished": "2024-02-28T08:13:15.310Z", "dateUpdated": "2026-05-11T13:45:47.021Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-11T13:45:47.021Z"}, "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."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["mm/shmem.c"], "versions": [{"version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "319116227e52d49eee671f0aa278bac89b3c1b69", "status": "affected", "versionType": "git"}, {"version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f", "status": "affected", "versionType": "git"}, {"version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43", "status": "affected", "versionType": "git"}, {"version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "140cfd9980124aecb6c03ef2e69c72d0548744de", "status": "affected", "versionType": "git"}, {"version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "ad53127973034c63b5348715a1043d0e80ceb330", "status": "affected", "versionType": "git"}, {"version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "2d59a0ed8b26b8f3638d8afc31f839e27759f1f6", "status": "affected", "versionType": "git"}, {"version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "7ed9d238c7dbb1fdb63ad96a6184985151b0171c", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["mm/shmem.c"], "versions": [{"version": "4.11", "status": "affected"}, {"version": "0", "lessThan": "4.11", "status": "unaffected", "versionType": "semver"}, {"version": "4.14.233", "lessThanOrEqual": "4.14.*", "status": "unaffected", "versionType": "semver"}, {"version": "4.19.191", "lessThanOrEqual": "4.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.4.120", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.38", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.11.22", "lessThanOrEqual": "5.11.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.12.5", "lessThanOrEqual": "5.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.13", "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": "4.11", "versionEndExcluding": "4.14.233"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.11", "versionEndExcluding": "4.19.191"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.11", "versionEndExcluding": "5.4.120"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.11", "versionEndExcluding": "5.10.38"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.11", "versionEndExcluding": "5.11.22"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.11", "versionEndExcluding": "5.12.5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.11", "versionEndExcluding": "5.13"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69"}, {"url": "https://git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f"}, {"url": "https://git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43"}, {"url": "https://git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de"}, {"url": "https://git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330"}, {"url": "https://git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6"}, {"url": "https://git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c"}], "title": "userfaultfd: release page in error path to avoid BUG_ON", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2024-06-21T16:28:01.611692Z", "id": "CVE-2021-46988", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-06-21T16:28:13.369Z"}}, {"providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-04T05:24:38.475Z"}, "title": "CVE Program Container", "references": [{"url": "https://git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c", "tags": ["x_transferred"]}]}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CVE Program Container", "references": [{"url": "https://git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c", "tags": ["x_transferred"]}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-04T05:24:38.475Z"}}, {"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2021-46988", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2024-06-21T16:28:01.611692Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2024-06-21T16:28:08.377Z"}}], "cna": {"title": "userfaultfd: release page in error path to avoid BUG_ON", "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "319116227e52d49eee671f0aa278bac89b3c1b69", "versionType": "git"}, {"status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f", "versionType": "git"}, {"status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43", "versionType": "git"}, {"status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "140cfd9980124aecb6c03ef2e69c72d0548744de", "versionType": "git"}, {"status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "ad53127973034c63b5348715a1043d0e80ceb330", "versionType": "git"}, {"status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "2d59a0ed8b26b8f3638d8afc31f839e27759f1f6", "versionType": "git"}, {"status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "lessThan": "7ed9d238c7dbb1fdb63ad96a6184985151b0171c", "versionType": "git"}], "programFiles": ["mm/shmem.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "4.11"}, {"status": "unaffected", "version": "0", "lessThan": "4.11", "versionType": "semver"}, {"status": "unaffected", "version": "4.14.233", "versionType": "semver", "lessThanOrEqual": "4.14.*"}, {"status": "unaffected", "version": "4.19.191", "versionType": "semver", "lessThanOrEqual": "4.19.*"}, {"status": "unaffected", "version": "5.4.120", "versionType": "semver", "lessThanOrEqual": "5.4.*"}, {"status": "unaffected", "version": "5.10.38", "versionType": "semver", "lessThanOrEqual": "5.10.*"}, {"status": "unaffected", "version": "5.11.22", "versionType": "semver", "lessThanOrEqual": "5.11.*"}, {"status": "unaffected", "version": "5.12.5", "versionType": "semver", "lessThanOrEqual": "5.12.*"}, {"status": "unaffected", "version": "5.13", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["mm/shmem.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69"}, {"url": "https://git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f"}, {"url": "https://git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43"}, {"url": "https://git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de"}, {"url": "https://git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330"}, {"url": "https://git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6"}, {"url": "https://git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c"}], "x_generator": {"engine": "bippy-1.2.0"}, "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."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "4.14.233", "versionStartIncluding": "4.11"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "4.19.191", "versionStartIncluding": "4.11"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.4.120", "versionStartIncluding": "4.11"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.10.38", "versionStartIncluding": "4.11"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.11.22", "versionStartIncluding": "4.11"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.12.5", "versionStartIncluding": "4.11"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.13", "versionStartIncluding": "4.11"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-11T13:45:47.021Z"}}}, "cveMetadata": {"cveId": "CVE-2021-46988", "state": "PUBLISHED", "dateUpdated": "2026-05-11T13:45:47.021Z", "dateReserved": "2024-02-27T18:42:55.948Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2024-02-28T08:13:15.310Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["mm/shmem.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "319116227e52d49eee671f0aa278bac89b3c1b69", "status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "versionType": "git"}, {"lessThan": "07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f", "status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "versionType": "git"}, {"lessThan": "b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43", "status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "versionType": "git"}, {"lessThan": "140cfd9980124aecb6c03ef2e69c72d0548744de", "status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "versionType": "git"}, {"lessThan": "ad53127973034c63b5348715a1043d0e80ceb330", "status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "versionType": "git"}, {"lessThan": "2d59a0ed8b26b8f3638d8afc31f839e27759f1f6", "status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "versionType": "git"}, {"lessThan": "7ed9d238c7dbb1fdb63ad96a6184985151b0171c", "status": "affected", "version": "cb658a453b9327ce96ce5222c24d162b5b65b564", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["mm/shmem.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "4.11"}, {"lessThan": "4.11", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "4.14.*", "status": "unaffected", "version": "4.14.233", "versionType": "semver"}, {"lessThanOrEqual": "4.19.*", "status": "unaffected", "version": "4.19.191", "versionType": "semver"}, {"lessThanOrEqual": "5.4.*", "status": "unaffected", "version": "5.4.120", "versionType": "semver"}, {"lessThanOrEqual": "5.10.*", "status": "unaffected", "version": "5.10.38", "versionType": "semver"}, {"lessThanOrEqual": "5.11.*", "status": "unaffected", "version": "5.11.22", "versionType": "semver"}, {"lessThanOrEqual": "5.12.*", "status": "unaffected", "version": "5.12.5", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "5.13", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "3CEB4F43-643B-4BF2-BC3B-FB797EC75463", "versionEndExcluding": "4.14.233", "versionStartIncluding": "4.11", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "5B6E6817-19A8-4C0A-8807-71DA48CF9191", "versionEndExcluding": "4.19.191", "versionStartIncluding": "4.15", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "2BDC71CF-4451-4D53-93E9-61DE7C4E25B0", "versionEndExcluding": "5.4.120", "versionStartIncluding": "4.20", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "2BB4E5E8-4AAD-475A-A1B9-F287254C7D72", "versionEndExcluding": "5.10.38", "versionStartIncluding": "5.5", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "83B53E9A-F426-4C03-9A5F-A931FF79827E", "versionEndExcluding": "5.11.22", "versionStartIncluding": "5.11", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "0274929A-B36C-4F4C-AB22-30A0DD6B995B", "versionEndExcluding": "5.12.5", "versionStartIncluding": "5.12", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:*", "matchCriteriaId": "0CBAD0FC-C281-4666-AB2F-F8E6E1165DF7", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "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."}], "id": "CVE-2021-46988", "lastModified": "2026-06-17T04:16:05.530", "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-2021-46988", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2024-06-21T16:28:01.611692Z", "version": "2.0.3"}}]}, "published": "2024-02-28T09:15:37.640", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/07c9b834c97d0fa3402fb7f3f3b32df370a6ff1f"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/140cfd9980124aecb6c03ef2e69c72d0548744de"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/2d59a0ed8b26b8f3638d8afc31f839e27759f1f6"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/319116227e52d49eee671f0aa278bac89b3c1b69"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7ed9d238c7dbb1fdb63ad96a6184985151b0171c"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/ad53127973034c63b5348715a1043d0e80ceb330"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b3f1731c6d7fbc1ebe3ed8eff6d6bec56d76ff43"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: userfaultfd: release page in error path to avoid BUG_ON", "id": "2266900", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2266900"}, "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-416", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nuserfaultfd: release page in error path to avoid BUG_ON\nConsider the following sequence of events:\n1. Userspace issues a UFFD ioctl, which ends up calling into\nshmem_mfill_atomic_pte(). We successfully account the blocks, we\nshmem_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\ndropping the mmap_lock, and retries, calling back into\nshmem_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\nimmediately returns - without releasing the page.\nThis triggers a BUG_ON in our caller, which asserts that the page\nshould always be consumed, unless -ENOENT is returned.\nTo fix this, detect if we have such a \"dangling\" page when accounting\nfails, and if so, release it before returning."], "name": "CVE-2021-46988", "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": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "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": "2024-02-28T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-46988\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-46988\nhttps://lore.kernel.org/linux-cve-announce/2024022825-CVE-2021-46988-ae47@gregkh/T/#u"], "threat_severity": "Low"}

{}