GHSA-7MQ9-8547-CP53
Vulnerability from github – Published: 2026-07-19 12:30 – Updated: 2026-07-24 15:32In 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.
{
"affected": [],
"aliases": [
"CVE-2026-63815"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-19T12:16:54Z",
"severity": "HIGH"
},
"details": "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.",
"id": "GHSA-7mq9-8547-cp53",
"modified": "2026-07-24T15:32:42Z",
"published": "2026-07-19T12:30:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63815"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/16bc237ce3c483b75575abea53cfb639745311ed"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2a9f9791653ba5ed3fb45bbffa8d63a7cd5cf706"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/378acf3cf19b6af6cba55e8dd1154c4e1504bae8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3c8d6b4093aea40a20596f452289e7c22d84e6d5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4ce2d52f680c1d8bfdad7cce05b815ea7ca9790d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/76e1a05cf6d4051931d7fa4ead51a05786a62918"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a08ee30dcbeff6b97df75c38c2589603ddde53a6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c3e05522daae4e7348a1ea81eeb321d25aa0fd3b"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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