{"dataType":"CVE_RECORD","cveMetadata":{"cveId":"CVE-2024-35949","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2024-05-17T13:50:33.134Z","datePublished":"2024-05-20T09:17:38.893Z","dateUpdated":"2026-08-05T11:31:08.601Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T11:31:08.601Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: make sure that WRITTEN is set on all metadata blocks\n\nWe previously would call btrfs_check_leaf() if we had the check\nintegrity code enabled, which meant that we could only run the extended\nleaf checks if we had WRITTEN set on the header flags.\n\nThis leaves a gap in our checking, because we could end up with\ncorruption on disk where WRITTEN isn't set on the leaf, and then the\nextended leaf checks don't get run which we rely on to validate all of\nthe item pointers to make sure we don't access memory outside of the\nextent buffer.\n\nHowever, since 732fab95abe2 (\"btrfs: check-integrity: remove\nCONFIG_BTRFS_FS_CHECK_INTEGRITY option\") we no longer call\nbtrfs_check_leaf() from btrfs_mark_buffer_dirty(), which means we only\never call it on blocks that are being written out, and thus have WRITTEN\nset, or that are being read in, which should have WRITTEN set.\n\nAdd checks to make sure we have WRITTEN set appropriately, and then make\nsure __btrfs_check_leaf() always does the item checking.  This will\nprotect us from file systems that have been corrupted and no longer have\nWRITTEN set on some of the blocks.\n\nThis was hit on a crafted image tweaking the WRITTEN bit and reported by\nKASAN as out-of-bound access in the eb accessors. The example is a dir\nitem at the end of an eb.\n\n  [2.042] BTRFS warning (device loop1): bad eb member start: ptr 0x3fff start 30572544 member offset 16410 size 2\n  [2.040] general protection fault, probably for non-canonical address 0xe0009d1000000003: 0000 [#1] PREEMPT SMP KASAN NOPTI\n  [2.537] KASAN: maybe wild-memory-access in range [0x0005088000000018-0x000508800000001f]\n  [2.729] CPU: 0 PID: 2587 Comm: mount Not tainted 6.8.2 #1\n  [2.729] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014\n  [2.621] RIP: 0010:btrfs_get_16+0x34b/0x6d0\n  [2.621] RSP: 0018:ffff88810871fab8 EFLAGS: 00000206\n  [2.621] RAX: 0000a11000000003 RBX: ffff888104ff8720 RCX: ffff88811b2288c0\n  [2.621] RDX: dffffc0000000000 RSI: ffffffff81dd8aca RDI: ffff88810871f748\n  [2.621] RBP: 000000000000401a R08: 0000000000000001 R09: ffffed10210e3ee9\n  [2.621] R10: ffff88810871f74f R11: 205d323430333737 R12: 000000000000001a\n  [2.621] R13: 000508800000001a R14: 1ffff110210e3f5d R15: ffffffff850011e8\n  [2.621] FS:  00007f56ea275840(0000) GS:ffff88811b200000(0000) knlGS:0000000000000000\n  [2.621] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n  [2.621] CR2: 00007febd13b75c0 CR3: 000000010bb50000 CR4: 00000000000006f0\n  [2.621] Call Trace:\n  [2.621]  <TASK>\n  [2.621]  ? show_regs+0x74/0x80\n  [2.621]  ? die_addr+0x46/0xc0\n  [2.621]  ? exc_general_protection+0x161/0x2a0\n  [2.621]  ? asm_exc_general_protection+0x26/0x30\n  [2.621]  ? btrfs_get_16+0x33a/0x6d0\n  [2.621]  ? btrfs_get_16+0x34b/0x6d0\n  [2.621]  ? btrfs_get_16+0x33a/0x6d0\n  [2.621]  ? __pfx_btrfs_get_16+0x10/0x10\n  [2.621]  ? __pfx_mutex_unlock+0x10/0x10\n  [2.621]  btrfs_match_dir_item_name+0x101/0x1a0\n  [2.621]  btrfs_lookup_dir_item+0x1f3/0x280\n  [2.621]  ? __pfx_btrfs_lookup_dir_item+0x10/0x10\n  [2.621]  btrfs_get_tree+0xd25/0x1910\n\n[ copy more details from report ]"}],"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 attack requires supplying a crafted btrfs image and having it mounted (or read) on the target — a local vector via loop device, udisks2/automount of removable media, or a user-mountable fstab entry. No network or remote peer parses this data.\nAC:L - Clearing the WRITTEN header bit and recomputing the block checksum is fully deterministic; the malformed dir item is dereferenced out of bounds on the very first lookup during mount, with no race or uncontrolled memory-layout precondition.\nPR:L - A local unprivileged account is sufficient on common deployments where udisks2/automount lets an active session mount an attacker-provided image or USB device; no root in the initial namespace is needed to place and mount the crafted filesystem.\nUI:N - The attacker performs the mount themselves (loop-mount or device insertion triggering automount); no separate victim has to act, and the crash/OOB happens during mount itself in `btrfs_lookup_dir_item()`.\nS:U - The out-of-bounds access and any resulting corruption stay within the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Skipping `check_dir_item()`/`check_extent_data()` lets attacker-controlled offsets index past `eb->folios[]`, turning an adjacent heap value into a `struct folio *` that is dereferenced — an effectively arbitrary kernel-memory read, and OOB item data (names, inline extents) can be copied back to userspace via readdir/getxattr/read.\nI:H - The same unvalidated offsets drive the `btrfs_set_*`/`write_extent_buffer()` and `memmove_extent_buffer()` paths — e.g. `btrfs_delete_one_dir_name()` underflows its length from an unchecked `name_len` — giving an out-of-bounds write through a wild folio pointer that is exploitable for control-flow hijacking.\nA:H - The reported result is an immediate general protection fault / KASAN wild-memory-access during mount (kernel oops), and the underflowed truncate path reaches a BUG(); the crash is reproducible on demand."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/tree-checker.c","fs/btrfs/tree-checker.h"],"versions":[{"version":"85d8a826c7cde17f9cca9c4debecb4538bdb6573","lessThan":"9dff3e36ea89e8003516841c27c45af562b6ef44","status":"affected","versionType":"git"},{"version":"85d8a826c7cde17f9cca9c4debecb4538bdb6573","lessThan":"ef3ba8ce8cf7075b716aa4afcefc3034215878ee","status":"affected","versionType":"git"},{"version":"85d8a826c7cde17f9cca9c4debecb4538bdb6573","lessThan":"e03418abde871314e1a3a550f4c8afb7b89cb273","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/tree-checker.c","fs/btrfs/tree-checker.h"],"versions":[{"version":"6.5","status":"affected"},{"version":"0","lessThan":"6.5","status":"unaffected","versionType":"semver"},{"version":"6.6.85","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.8.10","lessThanOrEqual":"6.8.*","status":"unaffected","versionType":"semver"},{"version":"6.9","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":"6.5","versionEndExcluding":"6.6.85"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.5","versionEndExcluding":"6.8.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.5","versionEndExcluding":"6.9"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/9dff3e36ea89e8003516841c27c45af562b6ef44"},{"url":"https://git.kernel.org/stable/c/ef3ba8ce8cf7075b716aa4afcefc3034215878ee"},{"url":"https://git.kernel.org/stable/c/e03418abde871314e1a3a550f4c8afb7b89cb273"}],"title":"btrfs: make sure that WRITTEN is set on all metadata blocks","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2024-06-17T17:38:20.543684Z","id":"CVE-2024-35949","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":"2024-06-17T17:40:35.661Z"}},{"providerMetadata":{"orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE","dateUpdated":"2024-08-02T03:21:48.957Z"},"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/ef3ba8ce8cf7075b716aa4afcefc3034215878ee","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/e03418abde871314e1a3a550f4c8afb7b89cb273","tags":["x_transferred"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OTB4HWU2PTVW5NEYHHLOCXDKG3PYA534/","tags":["x_transferred"]}]}]},"dataVersion":"5.2"}