{"id":"CVE-2025-21658","state":"PUBLISHED","title":"btrfs: avoid NULL pointer dereference if no valid extent tree","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: avoid NULL pointer dereference if no valid extent tree\n\n[BUG]\nSyzbot reported a crash with the following call trace:\n\n  BTRFS info (device loop0): scrub: started on devid 1\n  BUG: kernel NULL pointer dereference, address: 0000000000000208\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  PGD 106e70067 P4D 106e70067 PUD 107143067 PMD 0\n  Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI\n  CPU: 1 UID: 0 PID: 689 Comm: repro Kdump: loaded Tainted: G           O       6.13.0-rc4-custom+ #206\n  Tainted: [O]=OOT_MODULE\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022\n  RIP: 0010:find_first_extent_item+0x26/0x1f0 [btrfs]\n  Call Trace:\n   <TASK>\n   scrub_find_fill_first_stripe+0x13d/0x3b0 [btrfs]\n   scrub_simple_mirror+0x175/0x260 [btrfs]\n   scrub_stripe+0x5d4/0x6c0 [btrfs]\n   scrub_chunk+0xbb/0x170 [btrfs]\n   scrub_enumerate_chunks+0x2f4/0x5f0 [btrfs]\n   btrfs_scrub_dev+0x240/0x600 [btrfs]\n   btrfs_ioctl+0x1dc8/0x2fa0 [btrfs]\n   ? do_sys_openat2+0xa5/0xf0\n   __x64_sys_ioctl+0x97/0xc0\n   do_syscall_64+0x4f/0x120\n   entry_SYSCALL_64_after_hwframe+0x76/0x7e\n   </TASK>\n\n[CAUSE]\nThe reproducer is using a corrupted image where extent tree root is\ncorrupted, thus forcing to use \"rescue=all,ro\" mount option to mount the\nimage.\n\nThen it triggered a scrub, but since scrub relies on extent tree to find\nwhere the data/metadata extents are, scrub_find_fill_first_stripe()\nrelies on an non-empty extent root.\n\nBut unfortunately scrub_find_fill_first_stripe() doesn't really expect\nan NULL pointer for extent root, it use extent_root to grab fs_info and\ntriggered a NULL pointer dereference.\n\n[FIX]\nAdd an extra check for a valid extent root at the beginning of\nscrub_find_fill_first_stripe().\n\nThe new error path is introduced by 42437a6386ff (\"btrfs: introduce\nmount option rescue=ignorebadroots\"), but that's pretty old, and later\ncommit b979547513ff (\"btrfs: scrub: introduce helper to find and fill\nsector info for a scrub_stripe\") changed how we do scrub.\n\nSo for kernels older than 6.6, the fix will need manual backport.","publishedAt":"2025-01-21T12:18:14.578Z","updatedAt":"2026-10-30T12:20:41.665Z","severity":{"score":5.5,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","source":"CISA-ADP"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"42437a6386ffeaaf200731e73d723ea491f3fe7d","status":"affected","lessThan":"1fb37b7840fdcbf69d062a79d14afbf566b11873","versionType":"git"},{"version":"42437a6386ffeaaf200731e73d723ea491f3fe7d","status":"affected","lessThan":"24b85a8b0310e0144da9ab30be42e87e6476638a","versionType":"git"},{"version":"42437a6386ffeaaf200731e73d723ea491f3fe7d","status":"affected","lessThan":"aee5f69f3e6cd82bfefaca1b70b40b6cd8f3f784","versionType":"git"},{"version":"42437a6386ffeaaf200731e73d723ea491f3fe7d","status":"affected","lessThan":"6aecd91a5c5b68939cf4169e32bc49f3cd2dd329","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/scrub.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.11","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.72","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.10","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.13","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/scrub.c"]}],"references":["https://git.kernel.org/stable/c/1fb37b7840fdcbf69d062a79d14afbf566b11873","https://git.kernel.org/stable/c/24b85a8b0310e0144da9ab30be42e87e6476638a","https://git.kernel.org/stable/c/aee5f69f3e6cd82bfefaca1b70b40b6cd8f3f784","https://git.kernel.org/stable/c/6aecd91a5c5b68939cf4169e32bc49f3cd2dd329"],"weaknesses":["CWE-476"],"ingestedAt":"2026-10-30T12:38:04.623Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/21xxx/CVE-2025-21658.json","commit":"db8103c5921aac81d5d90efcf3745980dafabf49","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-21658","state":"PUBLISHED","datePublished":"2025-01-21T12:18:14.578Z","dateUpdated":"2026-10-30T12:20:41.665Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-12-29T08:45:45.731Z"},"containers":{"cna":{"title":"btrfs: avoid NULL pointer dereference if no valid extent tree","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: avoid NULL pointer dereference if no valid extent tree\n\n[BUG]\nSyzbot reported a crash with the following call trace:\n\n  BTRFS info (device loop0): scrub: started on devid 1\n  BUG: kernel NULL pointer dereference, address: 0000000000000208\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  PGD 106e70067 P4D 106e70067 PUD 107143067 PMD 0\n  Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI\n  CPU: 1 UID: 0 PID: 689 Comm: repro Kdump: loaded Tainted: G           O       6.13.0-rc4-custom+ #206\n  Tainted: [O]=OOT_MODULE\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022\n  RIP: 0010:find_first_extent_item+0x26/0x1f0 [btrfs]\n  Call Trace:\n   <TASK>\n   scrub_find_fill_first_stripe+0x13d/0x3b0 [btrfs]\n   scrub_simple_mirror+0x175/0x260 [btrfs]\n   scrub_stripe+0x5d4/0x6c0 [btrfs]\n   scrub_chunk+0xbb/0x170 [btrfs]\n   scrub_enumerate_chunks+0x2f4/0x5f0 [btrfs]\n   btrfs_scrub_dev+0x240/0x600 [btrfs]\n   btrfs_ioctl+0x1dc8/0x2fa0 [btrfs]\n   ? do_sys_openat2+0xa5/0xf0\n   __x64_sys_ioctl+0x97/0xc0\n   do_syscall_64+0x4f/0x120\n   entry_SYSCALL_64_after_hwframe+0x76/0x7e\n   </TASK>\n\n[CAUSE]\nThe reproducer is using a corrupted image where extent tree root is\ncorrupted, thus forcing to use \"rescue=all,ro\" mount option to mount the\nimage.\n\nThen it triggered a scrub, but since scrub relies on extent tree to find\nwhere the data/metadata extents are, scrub_find_fill_first_stripe()\nrelies on an non-empty extent root.\n\nBut unfortunately scrub_find_fill_first_stripe() doesn't really expect\nan NULL pointer for extent root, it use extent_root to grab fs_info and\ntriggered a NULL pointer dereference.\n\n[FIX]\nAdd an extra check for a valid extent root at the beginning of\nscrub_find_fill_first_stripe().\n\nThe new error path is introduced by 42437a6386ff (\"btrfs: introduce\nmount option rescue=ignorebadroots\"), but that's pretty old, and later\ncommit b979547513ff (\"btrfs: scrub: introduce helper to find and fill\nsector info for a scrub_stripe\") changed how we do scrub.\n\nSo for kernels older than 6.6, the fix will need manual backport."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"42437a6386ffeaaf200731e73d723ea491f3fe7d","status":"affected","lessThan":"1fb37b7840fdcbf69d062a79d14afbf566b11873","versionType":"git"},{"version":"42437a6386ffeaaf200731e73d723ea491f3fe7d","status":"affected","lessThan":"24b85a8b0310e0144da9ab30be42e87e6476638a","versionType":"git"},{"version":"42437a6386ffeaaf200731e73d723ea491f3fe7d","status":"affected","lessThan":"aee5f69f3e6cd82bfefaca1b70b40b6cd8f3f784","versionType":"git"},{"version":"42437a6386ffeaaf200731e73d723ea491f3fe7d","status":"affected","lessThan":"6aecd91a5c5b68939cf4169e32bc49f3cd2dd329","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/scrub.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.11","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.72","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.10","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.13","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/scrub.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/1fb37b7840fdcbf69d062a79d14afbf566b11873"},{"url":"https://git.kernel.org/stable/c/24b85a8b0310e0144da9ab30be42e87e6476638a"},{"url":"https://git.kernel.org/stable/c/aee5f69f3e6cd82bfefaca1b70b40b6cd8f3f784"},{"url":"https://git.kernel.org/stable/c/6aecd91a5c5b68939cf4169e32bc49f3cd2dd329"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:20:41.665Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.6.72"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.12.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.13"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"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"}},{"other":{"type":"ssvc","content":{"id":"CVE-2025-21658","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2025-10-01T19:52:37.080379Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-476","lang":"en","type":"CWE","description":"CWE-476 NULL Pointer Dereference"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2025-10-01T19:57:13.496Z"}}]}}}