{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2026-89493", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-89493", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-09-11T19:43:44.803Z", "updatedAt": "2026-10-19T08:47:44.950Z", "importedAt": "2026-10-24T01:58:35.090Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "ocfs2: validate rl_used against rl_count in refcount block validator", "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nocfs2: validate rl_used against rl_count in refcount block validator\n\nocfs2_find_refcount_rec_in_rl() walks the on-disk refcount record array\nwith:\n\n\tfor (; i < le16_to_cpu(rb->rf_records.rl_used); i++) {\n\t\trec = &rb->rf_records.rl_recs[i];\n\t\t...\n\nrl_recs[] lives in a single metadata block (4096 bytes on the common\nconfiguration), so its real capacity is fixed by\nocfs2_refcount_recs_per_rb(sb) (247 records for a 4K block with the\n16-byte ocfs2_refcount_rec). rl_used and rl_count are both read directly\noff disk by ocfs2_validate_refcount_block() and are never checked against\nthat capacity, nor against each other, before any refcount/reflink/CoW\noperation walks the array.\n\nA crafted (or corrupted) refcount block with rl_used == 0xffff makes the\nloop above walk far past the end of the block, dereferencing rl_recs[i]\nfor i up to 65534. The resulting index is then handed to the sibling\nocfs2_insert_refcount_rec(), whose insert-shift does:\n\n\tif (index < le16_to_cpu(rf_list->rl_used))\n\t\tmemmove(&rf_list->rl_recs[index + 1],\n\t\t\t&rf_list->rl_recs[index],\n\t\t\t(le16_to_cpu(rf_list->rl_used) - index) *\n\t\t\t sizeof(struct ocfs2_refcount_rec));\n\ni.e. a memmove() of up to (0xffff - index) * 16 bytes (~1 MiB) from an\noffset already past the block. This is reachable from an ordinary reflink\n(FICLONE) against a crafted/corrupted ocfs2 image: attaching an extent\nwhose cpos sorts past every real record in the leaf forces the lookup to\nrun off the end instead of returning early on a match. The attacker model\nis local: CAP_SYS_ADMIN mounting a crafted or corrupted ocfs2 image, or a\nraw write to the block device backing an already-mounted ocfs2 filesystem.\n\nocfs2_validate_refcount_block() already validates the block's ECC,\nsignature, rf_blkno and rf_fs_generation, but never rl_count/rl_used\nagainst the block's actual on-disk capacity. This is the same class of\ngap that ocfs2_validate_extent_block() (fs/ocfs2/alloc.c) already closes\nfor the sibling extent-list header, which checks both the record capacity\nand the \"used\" bound before any code walks h_list.l_recs[]:\n\n\tif (le16_to_cpu(eb->h_list.l_count) != ocfs2_extent_recs_per_eb(sb)) {\n\t\trc = ocfs2_error(...);\n\t\tgoto bail;\n\t}\n\n\tif (le16_to_cpu(eb->h_list.l_next_free_rec) >\n\t le16_to_cpu(eb->h_list.l_count)) {\n\t\trc = ocfs2_error(...);\n\t\tgoto bail;\n\t}\n\nAdd the equivalent pair of checks to ocfs2_validate_refcount_block():\nreject a refcount block whose rl_count does not match the fixed per-block\ncapacity returned by ocfs2_refcount_recs_per_rb(), and reject rl_used >\nrl_count. Both checks are skipped when OCFS2_REFCOUNT_TREE_FL is set,\nbecause in that case the same union bytes hold an ocfs2_extent_list\n(rf_list), not the refcount record list (rf_records) -- that layout is\nalready validated separately by ocfs2_validate_extent_block() when the\nreferenced extent block is read. This mirrors the existing\n\"!(rb->rf_flags & OCFS2_REFCOUNT_TREE_FL)\" guard used elsewhere in this\nfile (e.g. ocfs2_get_refcount_rec()) to decide whether rf_records or\nrf_list is the live member of the union.\n\nWith this in place, a forged rl_used/rl_count is caught at block\nvalidation time (ocfs2_error()), consistent with every other corruption\ncheck in this function, instead of driving an out-of-bounds read in\nocfs2_find_refcount_rec_in_rl() and a subsequent out-of-bounds memmove()\nin ocfs2_insert_refcount_rec().\n\nVerified against a crafted image on a v6.19 KASAN (KASAN_GENERIC) build:\nreplaying the same reflink (FICLONE) reliably hit a KASAN report in\n__ocfs2_increase_refcount()/ocfs2_insert_refcount_rec() before this patch,\nand triggers no report once ocfs2_validate_refcount_block() rejects the\nforged rl_used/rl_count.", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4", "status": "affected", "versionType": "git", "lessThan": "f882e9e32d017a6569b2996c63ba3864717788e6" }, { "version": "f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4", "status": "affected", "versionType": "git", "lessThan": "5593b63028cb43a6cda75a65ce1db95f00ea6857" }, { "version": "f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4", "status": "affected", "versionType": "git", "lessThan": "c8b02f4ee91e757b3fff556c7168b24b7ae55132" }, { "version": "f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4", "status": "affected", "versionType": "git", "lessThan": "97584e93fc49a2d59252ac60467e9279f11b1b5b" }, { "version": "f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4", "status": "affected", "versionType": "git", "lessThan": "af56e90cb546cb0c47bef059335365283f61d6a4" }, { "version": "f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4", "status": "affected", "versionType": "git", "lessThan": "0761d2c9494424469a0d30a9da3496ca010b0b2d" }, { "version": "f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4", "status": "affected", "versionType": "git", "lessThan": "04ead708e13ddcb9c39319cbe02a18cef99cb823" }, { "version": "f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4", "status": "affected", "versionType": "git", "lessThan": "4ca62df6bc0708947b48da3f6a712ecb8e73929c" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "2.6.32", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "2.6.32" }, { "version": "5.10.270", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.10.*" }, { "version": "5.15.221", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.15.*" }, { "version": "6.1.188", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.157", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.109", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.50", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "7.2.4", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "7.2.*" }, { "version": "7.3", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }