FROMLIST: libdft: fdt_next_tag: Harden offset overflow check

As 'offset' is obtained through various paths within the function by
adding user-provided values to 'startoffset' and as we validate its
final value by substracting it from the initial one, there is a risk
that one of the paths might have lead to an overflow, making the check
validate a "negative" (wrong) length, potentially causing fdt_next_tag()
to report an invalid offset as valid through 'nextoffset'.

For example, when parsing an FDT_PROP, we currently validate that

    offset = startoffset + len + FDT_TAGSIZE

doesn't overflow but then assign

    offset = startoffset + len + sizeof(struct fdt_property)

so harden all paths by validating the offset in the very last check.

Signed-off-by: Pierre-Clément Tosi <ptosi@google.com>

(am from https://lore.kernel.org/devicetree-compiler/20231011172427.g4tlsew3wsjtddil@google.com/)

Test: N/A
Change-Id: I0b17b0827ccc0ece0a2d1795b388408fb599aed7

0 files changed, 0 insertions, 0 deletions