CVE-2026-74350: ocfs2: validate fast symlink target during inode read

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

ocfs2: validate fast symlink target during inode read

ocfs2validateinodeblock() already rejects several inconsistent self-contained dinodes before they are exposed to the rest of the filesystem. Fast symlinks need the same treatment.

A zero-cluster symlink is treated as a fast symlink and later read through pagegetlink() and ocfs2fastsymlinkreadfolio(). That path uses strnlen() on the inline payload and then copies len + 1 bytes into the folio. If a corrupt dinode stores an isize that does not fit the inline area or omits the terminating NUL at isize, that copy reads past the end of the inode block buffer.

Reject zero-cluster symlink dinodes whose isize exceeds the inline fast-symlink capacity or whose inline payload is not NUL-terminated exactly at isize when the inode block is validated. This keeps malformed fast symlinks from reaching the read path.

Validation reproduced this kernel report: KASAN use-after-free in ocfs2fastsymlinkreadfolio+0x12c/0x1f0 RIP: 0033:0x7f5c6d859aa7 Read of size 3905 Call trace: dumpstacklvl+0x66/0xa0 (?:?) printreport+0xce/0x630 (?:?) ocfs2fastsymlinkreadfolio+0x12c/0x1f0 (fs/ocfs2/inode.c:?) srsoaliasreturnthunk+0x5/0xfbef5 (?:?) virtaddrvalid+0x19f/0x330 (?:?) kasanreport+0xe0/0x110 (?:?) kasancheckrange+0x105/0x1b0 (?:?) asanmemcpy+0x23/0x60 (?:?) filemapreadfolio+0x27/0xe0 (?:?) filemapreadfolio+0x35/0xe0 (?:?) doreadcachefolio+0x138/0x230 (?:?) pagegetlink+0x26/0x110 (?:?) pagegetlink+0x2e/0x70 (?:?) vfsreadlink+0x15e/0x250 (?:?) touchatime+0x4d/0x370 (?:?) doreadlinkat+0x186/0x200 (?:?) douseraddrfault+0x65a/0x890 (?:?) x64sysreadlink+0x46/0x60 (?:?) dosyscall64+0x115/0x6a0 (arch/x86/entry/syscall64.c:87) entrySYSCALL64afterhwframe+0x77/0x7f (?:?)