[klibc] cpio: Fix possible integer overflow on 32-bit systems

The maximum name and file sizes in the "new" header format are 32-bit
unsigned values.  However, the I/O functions mostly use long for sizes
and offsets, so that sizes >= 2^31 are handled wrongly on 32-bit
systems.

The current GNU cpio code doesn't seem to have this problem, but the
divergence between this version and that is large enough that I can't
simply cherry-pick a fix for it.

As a short-term fix, in read_in_new_ascii(), fail if c_namesize or
c_filesize is > LONG_MAX.

CVE-2021-31872

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
1 file changed