CVE-2026-63815

In the Linux kernel, the following vulnerability has been resolved:

f2fs: bound iinlinexattr_size for non-inline-xattr inodes

When the flexibleinlinexattr feature is enabled, doreadinode() loads the on-disk iinlinexattr_size unconditionally:

if (f2fs_sb_has_flexible_inline_xattr(sbi))
    fi->i_inline_xattr_size = le16_to_cpu(ri->i_inline_xattr_size);

but sanitycheckinode() only range-checks it when the inode also has the FIINLINEXATTR flag set. An inode that carries an inline dentry or inline data but not FIINLINEXATTR -- the normal layout for an inline directory -- therefore keeps a fully attacker-controlled iinlinexattr_size from a crafted image.

getinlinexattr_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 iinlinexattrsize drives MAXINLINEDATA() and NRINLINEDENTRY() negative, so makedentryptrinline() 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 f2fsfilldentries(); the same underflow also corrupts ADDRSPERINODE for regular files.

Validate iinlinexattrsize against MAXINLINEXATTRSIZE whenever the flexibleinlinexattr feature is enabled -- i.e. whenever the value is loaded from disk and consumed -- and keep the lower MININLINEXATTRSIZE bound gated on inodes that actually carry an inline xattr, so legitimate inodes with iinlinexattrsize == 0 are still accepted.