sqfs_frag_lookup() reads a 16-bit metadata block header whose lower
15 bits encode the data size. Unlike sqfs_read_metablock() in
sqfs_inode.c, this function does not validate that the decoded size is
within SQFS_METADATA_BLOCK_SIZE (8192). A malformed SquashFS image can
set the size field to any value up to 32767, causing memcpy to write
past the 8192-byte 'entries' heap buffer.
Add the same bounds check used by sqfs_read_metablock(): reject any
metadata block header with SQFS_METADATA_SIZE(header) exceeding
SQFS_METADATA_BLOCK_SIZE.
Found by fuzzing with libFuzzer + AddressSanitizer.
Signed-off-by: Eric Kilmer <eric.kilmer@trailofbits.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Eric KilmerandTom Rini
e365a269df