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() doesn't 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 doesn't check if it's 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 doesn't match expected

For thread records, check against HFSPLUS_MIN_THREAD_SZ before reading
nodeName.length to avoid reading uninitialized data at call sites that
don't 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.