CVE-2026-46169

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

hfsplus: fix uninit-value by validating catalog record size

Syzbot reported a KMSAN uninit-value issue in hfsplus_strcasecmp(). The root cause is that hfs_brec_read() doesnt validate that the on-disk record size matches the expected size for the record type being read.

When mounting a corrupted filesystem, hfs_brec_read() may read less data than expected. For example, when reading a catalog thread record, the debug output showed:

HFSPLUS_BREC_READ: rec_len=520, fd->entrylength=26 HFSPLUS_BREC_READ: WARNING - entrylength (26) < rec_len (520) - PARTIAL READ!

hfs_brec_read() only validates that entrylength is not greater than the buffer size, but doesnt check if its less than expected. It successfully reads 26 bytes into a 520-byte structure and returns success, leaving 494 bytes uninitialized.

This uninitialized data in tmp.thread.nodeName then gets copied by hfsplus_cat_build_key_uni() and used by hfsplus_strcasecmp(), triggering the KMSAN warning when the uninitialized bytes are used as array indices in case_fold().

Fix by introducing hfsplus_brec_read_cat() wrapper that:

1. Calls hfs_brec_read() to read the data
2. Validates the record size based on the type field:
   • Fixed size for folder and file records
   • Variable size for thread records (depends on string length)
3. Returns -EIO if size doesnt match expected

For thread records, check against HFSPLUS_MIN_THREAD_SZ before reading nodeName.length to avoid reading uninitialized data at call sites that dont zero-initialize the entry structure.

Also initialize the tmp variable in hfsplus_find_cat() as defensive programming to ensure no uninitialized data even if validation is bypassed.

Weakness

The product uses or accesses a resource that has not been initialized.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/3003dbf62d151d47a6b90f71655292a51a05f244
• https://git.kernel.org/stable/c/3bc337697c66db2e2a4a94f0509c282c1a014b86
• https://git.kernel.org/stable/c/61a790974ff7e533acbceca06c7d02f22bf96d4d
• https://git.kernel.org/stable/c/8be69532e399eec9d9d990f6958b4ff2383b19b3
• https://git.kernel.org/stable/c/93e8d613f1a01b6637f387cc93f184cf7fb881d6
• https://git.kernel.org/stable/c/a420904450962a562ad053a41a53a27755021b48
• https://git.kernel.org/stable/c/b6b592275aeff184aa82fcf6abccd833fb71b393
• https://git.kernel.org/stable/c/c91bbd6193c70a02c50c22e0fb1f60c3c5bd053a