CVE-2026-63815 (GCVE-0-2026-63815)
Vulnerability from cvelistv5
Published
2026-07-19 12:02
Modified
2026-08-17 04:51
Severity ?
8.4 (High) - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: bound i_inline_xattr_size for non-inline-xattr inodes When the flexible_inline_xattr feature is enabled, do_read_inode() loads the on-disk i_inline_xattr_size unconditionally: if (f2fs_sb_has_flexible_inline_xattr(sbi)) fi->i_inline_xattr_size = le16_to_cpu(ri->i_inline_xattr_size); but sanity_check_inode() only range-checks it when the inode also has the FI_INLINE_XATTR flag set. An inode that carries an inline dentry or inline data but not FI_INLINE_XATTR -- the normal layout for an inline directory -- therefore keeps a fully attacker-controlled i_inline_xattr_size from a crafted image. get_inline_xattr_addrs() returns that value with no flag gating, so it feeds the inode geometry: MAX_INLINE_DATA() = 4 * (CUR_ADDRS_PER_INODE - i_inline_xattr_size - 1) NR_INLINE_DENTRY() = MAX_INLINE_DATA() * BITS_PER_BYTE / (...) addrs_per_page() = CUR_ADDRS_PER_INODE - i_inline_xattr_size A large i_inline_xattr_size drives MAX_INLINE_DATA() and NR_INLINE_DENTRY() negative, so make_dentry_ptr_inline() sets d->max (int) to a negative value. The inline directory walk then compares an unsigned long bit_pos against that negative d->max, which is promoted to a huge unsigned bound, and reads far past the inline area: while (bit_pos < d->max) /* fs/f2fs/dir.c */ ... test_bit_le(bit_pos, d->bitmap) / d->dentry[bit_pos] ... Mounting a crafted image and reading such a directory triggers an out-of-bounds read in f2fs_fill_dentries(); the same underflow also corrupts ADDRS_PER_INODE for regular files. Validate i_inline_xattr_size against MAX_INLINE_XATTR_SIZE whenever the flexible_inline_xattr feature is enabled -- i.e. whenever the value is loaded from disk and consumed -- and keep the lower MIN_INLINE_XATTR_SIZE bound gated on inodes that actually carry an inline xattr, so legitimate inodes with i_inline_xattr_size == 0 are still accepted.
References
Impacted products
Vendor Product Version
Linux Linux Version: 6afc662e68b5f988282ff20afd58a89b1c279dca
Version: 6afc662e68b5f988282ff20afd58a89b1c279dca
Version: 6afc662e68b5f988282ff20afd58a89b1c279dca
Version: 6afc662e68b5f988282ff20afd58a89b1c279dca
Version: 6afc662e68b5f988282ff20afd58a89b1c279dca
Version: 6afc662e68b5f988282ff20afd58a89b1c279dca
Version: 6afc662e68b5f988282ff20afd58a89b1c279dca
Version: 6afc662e68b5f988282ff20afd58a89b1c279dca
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/f2fs/inode.c"
          ],
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          "vendor": "Linux",
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          "product": "Linux",
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "4.15"
            },
            {
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "version": "5.15.212",
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            },
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              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.178",
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              "version": "6.6.145",
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            },
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              "status": "unaffected",
              "version": "6.12.96",
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            },
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              "status": "unaffected",
              "version": "6.18.39",
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              "status": "unaffected",
              "version": "7.1.3",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "vulnerable": true
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                  "vulnerable": true
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                  "versionEndExcluding": "7.2",
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                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: bound i_inline_xattr_size for non-inline-xattr inodes\n\nWhen the flexible_inline_xattr feature is enabled, do_read_inode() loads\nthe on-disk i_inline_xattr_size unconditionally:\n\n\tif (f2fs_sb_has_flexible_inline_xattr(sbi))\n\t\tfi-\u003ei_inline_xattr_size = le16_to_cpu(ri-\u003ei_inline_xattr_size);\n\nbut sanity_check_inode() only range-checks it when the inode also has the\nFI_INLINE_XATTR flag set.  An inode that carries an inline dentry or inline\ndata but not FI_INLINE_XATTR -- the normal layout for an inline\ndirectory -- therefore keeps a fully attacker-controlled\ni_inline_xattr_size from a crafted image.\n\nget_inline_xattr_addrs() returns that value with no flag gating, so it\nfeeds the inode geometry:\n\n\tMAX_INLINE_DATA()  = 4 * (CUR_ADDRS_PER_INODE - i_inline_xattr_size - 1)\n\tNR_INLINE_DENTRY() = MAX_INLINE_DATA() * BITS_PER_BYTE / (...)\n\taddrs_per_page()   = CUR_ADDRS_PER_INODE - i_inline_xattr_size\n\nA large i_inline_xattr_size drives MAX_INLINE_DATA() and NR_INLINE_DENTRY()\nnegative, so make_dentry_ptr_inline() sets d-\u003emax (int) to a negative\nvalue.  The inline directory walk then compares an unsigned long bit_pos\nagainst that negative d-\u003emax, which is promoted to a huge unsigned bound,\nand reads far past the inline area:\n\n\twhile (bit_pos \u003c d-\u003emax)\t\t/* fs/f2fs/dir.c */\n\t\t... test_bit_le(bit_pos, d-\u003ebitmap) / d-\u003edentry[bit_pos] ...\n\nMounting a crafted image and reading such a directory triggers an\nout-of-bounds read in f2fs_fill_dentries(); the same underflow also\ncorrupts ADDRS_PER_INODE for regular files.\n\nValidate i_inline_xattr_size against MAX_INLINE_XATTR_SIZE whenever the\nflexible_inline_xattr feature is enabled -- i.e. whenever the value is\nloaded from disk and consumed -- and keep the lower MIN_INLINE_XATTR_SIZE\nbound gated on inodes that actually carry an inline xattr, so legitimate\ninodes with i_inline_xattr_size == 0 are still accepted."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.4,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires local syscalls (mount on a block/loop device, then getdents/lookup on an inline directory); f2fs is not reachable via a network-facing in-kernel protocol handler.\nAC:L - The attacker fully controls the on-disk inode fields in a crafted f2fs image and can reliably trigger the bug by mounting that image and reading the directory; no race or rare runtime state is required.\nPR:N - An attacker can craft a malicious f2fs image offline with no privileges on the target system; exploitation is triggered when the image is mounted and its inline directory is read, including by privileged auto-mount services on shared/kiosk systems.\nUI:N - No victim user action beyond the attacker\u0027s own mount and directory read is required; an attacker with user-namespace mount capability can self-trigger without involving another user.\nS:U - Impact is kernel memory corruption and information disclosure within the same kernel security boundary, not a cross-boundary escape such as guest-to-host VM breakout.\nC:H - The corrupted geometry drives out-of-bounds reads via test_bit_le(), dentry, and filename pointer accesses far beyond the inline data area, enabling kernel memory disclosure.\nI:H - Integer underflow in inode geometry also corrupts ADDRS_PER_INODE/addrs_per_page calculations for regular files, creating memory corruption that can be leveraged for out-of-bounds writes and further exploitation.\nA:H - Reading far past the inline area can cause kernel oops or panic, and the corrupted address calculations can crash or destabilize the kernel during subsequent file operations."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:51:22.389Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/3c8d6b4093aea40a20596f452289e7c22d84e6d5"
        },
        {
          "url": "https://git.kernel.org/stable/c/a08ee30dcbeff6b97df75c38c2589603ddde53a6"
        },
        {
          "url": "https://git.kernel.org/stable/c/c3e05522daae4e7348a1ea81eeb321d25aa0fd3b"
        },
        {
          "url": "https://git.kernel.org/stable/c/76e1a05cf6d4051931d7fa4ead51a05786a62918"
        },
        {
          "url": "https://git.kernel.org/stable/c/2a9f9791653ba5ed3fb45bbffa8d63a7cd5cf706"
        },
        {
          "url": "https://git.kernel.org/stable/c/4ce2d52f680c1d8bfdad7cce05b815ea7ca9790d"
        },
        {
          "url": "https://git.kernel.org/stable/c/16bc237ce3c483b75575abea53cfb639745311ed"
        },
        {
          "url": "https://git.kernel.org/stable/c/378acf3cf19b6af6cba55e8dd1154c4e1504bae8"
        }
      ],
      "title": "f2fs: bound i_inline_xattr_size for non-inline-xattr inodes",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63815",
    "datePublished": "2026-07-19T12:02:15.345Z",
    "dateReserved": "2026-07-19T07:54:57.014Z",
    "dateUpdated": "2026-08-17T04:51:22.389Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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