commonlib/cbfs: Fix minor parser edge cases

This patch fixes a few minor CBFS parsing edge cases that could lead to
unintended behavior: the CBFS attribute parser could have run into an
infinite loop if an attribute's length was (accidentally or maliciously)
invalid. A length of 0 would have caused it to read the same attribute
over and over again without making forward progress, while a very large
length could have caused an overflow that makes it go backwards to find
the next attribute. Also, the filename was not guaranteed to be
null-terminated which could have resulted in out-of-bounds reads on a
few error messages.

Finally, clarify the validity guarantees for CBFS header fields offered
by cbfs_walk() in the comment explaining cbfs_mdata.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: Ie569786e5bec355b522f6580f53bdd8b16a4d726
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57569
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jakub Czapiga <jacz@semihalf.com>

0 files changed, 0 insertions, 0 deletions