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:
- Calls hfs_brec_read() to read the data
- 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)
- 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.