{"id":"CVE-2024-49854","state":"PUBLISHED","title":"block, bfq: fix uaf for accessing waker_bfqq after splitting","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nblock, bfq: fix uaf for accessing waker_bfqq after splitting\n\nAfter commit 42c306ed7233 (\"block, bfq: don't break merge chain in\nbfq_split_bfqq()\"), if the current procress is the last holder of bfqq,\nthe bfqq can be freed after bfq_split_bfqq(). Hence recored the bfqq and\nthen access bfqq->waker_bfqq may trigger UAF. What's more, the waker_bfqq\nmay in the merge chain of bfqq, hence just recored waker_bfqq is still\nnot safe.\n\nFix the problem by adding a helper bfq_waker_bfqq() to check if\nbfqq->waker_bfqq is in the merge chain, and current procress is the only\nholder.","publishedAt":"2024-10-21T12:18:46.723Z","updatedAt":"2026-08-05T11:40:04.538Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e0c20d88b7dce85d2703bb6ba77bf359959675cd","status":"affected","lessThan":"63a07379fdb6c72450cb05294461c6016b8b7726","versionType":"git"},{"version":"de6c5e3a456019d2182e345730e59721714fa0b5","status":"affected","lessThan":"de0456460f2abf921e356ed2bd8da87a376680bd","versionType":"git"},{"version":"19f3bec2ac4be329b9bd12b18a989b867618d2d8","status":"affected","lessThan":"0780451f03bf518bc032a7c584de8f92e2d39d7f","versionType":"git"},{"version":"13b3d0e8cb121f99b11918a0d4bcc1ce4647d352","status":"affected","lessThan":"0b8bda0ff17156cd3f60944527c9d8c9f99f1583","versionType":"git"},{"version":"4780f50ea50cfe8e89fc3747bf3dd155488433bb","status":"affected","lessThan":"cae58d19121a70329cf971359e2518c93fec04fe","versionType":"git"},{"version":"42c306ed723321af4003b2a41bb73728cab54f85","status":"affected","lessThan":"1ba0403ac6447f2d63914fb760c44a3b19c44eaf","versionType":"git"},{"version":"9e813033594b141f61ff0ef0cfaaef292564b041","status":"affected","versionType":"git"},{"version":"3a5f45a4ad4e1fd36b0a998eef03d76a4f02a2a8","status":"affected","versionType":"git"},{"version":"3630a18846c7853aa326d3b42fd0a855af7b41bc","status":"affected","versionType":"git"},{"version":"4.19.323","status":"affected","lessThan":"4.20","versionType":"semver"},{"version":"5.4.285","status":"affected","lessThan":"5.5","versionType":"semver"},{"version":"5.10.227","status":"affected","lessThan":"5.11","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["block/bfq-iosched.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["block/bfq-iosched.c"]}],"references":["https://git.kernel.org/stable/c/63a07379fdb6c72450cb05294461c6016b8b7726","https://git.kernel.org/stable/c/de0456460f2abf921e356ed2bd8da87a376680bd","https://git.kernel.org/stable/c/0780451f03bf518bc032a7c584de8f92e2d39d7f","https://git.kernel.org/stable/c/0b8bda0ff17156cd3f60944527c9d8c9f99f1583","https://git.kernel.org/stable/c/cae58d19121a70329cf971359e2518c93fec04fe","https://git.kernel.org/stable/c/1ba0403ac6447f2d63914fb760c44a3b19c44eaf","https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html"],"weaknesses":[],"ingestedAt":"2026-10-29T20:07:56.516Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2024/49xxx/CVE-2024-49854.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2024-49854","state":"PUBLISHED","datePublished":"2024-10-21T12:18:46.723Z","dateUpdated":"2026-08-05T11:40:04.538Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-10-21T12:17:06.016Z"},"containers":{"cna":{"title":"block, bfq: fix uaf for accessing waker_bfqq after splitting","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nblock, bfq: fix uaf for accessing waker_bfqq after splitting\n\nAfter commit 42c306ed7233 (\"block, bfq: don't break merge chain in\nbfq_split_bfqq()\"), if the current procress is the last holder of bfqq,\nthe bfqq can be freed after bfq_split_bfqq(). Hence recored the bfqq and\nthen access bfqq->waker_bfqq may trigger UAF. What's more, the waker_bfqq\nmay in the merge chain of bfqq, hence just recored waker_bfqq is still\nnot safe.\n\nFix the problem by adding a helper bfq_waker_bfqq() to check if\nbfqq->waker_bfqq is in the merge chain, and current procress is the only\nholder."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e0c20d88b7dce85d2703bb6ba77bf359959675cd","status":"affected","lessThan":"63a07379fdb6c72450cb05294461c6016b8b7726","versionType":"git"},{"version":"de6c5e3a456019d2182e345730e59721714fa0b5","status":"affected","lessThan":"de0456460f2abf921e356ed2bd8da87a376680bd","versionType":"git"},{"version":"19f3bec2ac4be329b9bd12b18a989b867618d2d8","status":"affected","lessThan":"0780451f03bf518bc032a7c584de8f92e2d39d7f","versionType":"git"},{"version":"13b3d0e8cb121f99b11918a0d4bcc1ce4647d352","status":"affected","lessThan":"0b8bda0ff17156cd3f60944527c9d8c9f99f1583","versionType":"git"},{"version":"4780f50ea50cfe8e89fc3747bf3dd155488433bb","status":"affected","lessThan":"cae58d19121a70329cf971359e2518c93fec04fe","versionType":"git"},{"version":"42c306ed723321af4003b2a41bb73728cab54f85","status":"affected","lessThan":"1ba0403ac6447f2d63914fb760c44a3b19c44eaf","versionType":"git"},{"version":"9e813033594b141f61ff0ef0cfaaef292564b041","status":"affected","versionType":"git"},{"version":"3a5f45a4ad4e1fd36b0a998eef03d76a4f02a2a8","status":"affected","versionType":"git"},{"version":"3630a18846c7853aa326d3b42fd0a855af7b41bc","status":"affected","versionType":"git"},{"version":"4.19.323","status":"affected","lessThan":"4.20","versionType":"semver"},{"version":"5.4.285","status":"affected","lessThan":"5.5","versionType":"semver"},{"version":"5.10.227","status":"affected","lessThan":"5.11","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["block/bfq-iosched.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["block/bfq-iosched.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/63a07379fdb6c72450cb05294461c6016b8b7726"},{"url":"https://git.kernel.org/stable/c/de0456460f2abf921e356ed2bd8da87a376680bd"},{"url":"https://git.kernel.org/stable/c/0780451f03bf518bc032a7c584de8f92e2d39d7f"},{"url":"https://git.kernel.org/stable/c/0b8bda0ff17156cd3f60944527c9d8c9f99f1583"},{"url":"https://git.kernel.org/stable/c/cae58d19121a70329cf971359e2518c93fec04fe"},{"url":"https://git.kernel.org/stable/c/1ba0403ac6447f2d63914fb760c44a3b19c44eaf"}],"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"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable code is the BFQ I/O scheduler in the block layer, reached only by submitting I/O locally (read/write/ioctl on a file or block device backed by a bfq-scheduled queue). No network or physical vector exists.\nAC:L - The attacker fully controls both the queue-merge topology and the split trigger by spawning cooperating processes doing interleaved then seeky I/O; this is not a race requiring uncontrolled timing, and syzkaller reproduced the identical UAF with a generic fsstress workload on a default distro-common BFQ configuration.\nPR:L - Any unprivileged local user able to issue ordinary filesystem I/O can reach bfq_init_rq(); no capabilities, root, or namespace tricks are needed.\nUI:N - The attacker's own processes create the merged/waker queue state and trigger the split; no victim action or interaction is required.\nS:U - The corruption is confined to kernel heap objects within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - The bug reads a pointer out of a freed bfq_queue slab object, and that value is then dereferenced and propagated; with the freed slot refilled by attacker-created bfq_queues this becomes a controlled kernel-memory read primitive and kernel pointer disclosure.\nI:H - hlist_add_head() writes list pointers into the freed/attacker-influenced waker_bfqq object, and leaves a live queue linked into a dead object's woken_list that is traversed later — a write-what-where style primitive leveragable for privilege escalation.\nA:H - The use-after-free reliably produces slab corruption and a kernel oops/panic, as demonstrated by the KASAN slab-use-after-free report from the same code path."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T11:40:04.538Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.19.323"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4.285"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10.227"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2024-49854","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2024-10-21T12:56:32.405058Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-10-21T13:04:11.371Z"}},{"title":"CVE Program Container","references":[{"url":"https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html"}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2025-11-03T22:22:22.684Z"}}]}}}