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authorJacob Garber <jgarber1@ualberta.ca>2019-07-02 14:38:38 -0600
committerMartin Roth <martinroth@google.com>2019-07-07 20:59:04 +0000
commit2d58bf6a037c8ad474db4a902e799bee637e7ec0 (patch)
tree049fba76fd9d23f5281dc95e70e5e87acde7a901 /src/arch/mips/Kconfig
parent96e0ce30dbcdf709c92ef40ca9cfee0895b712ac (diff)
util/cbfstool: Prevent overflow of 16 bit multiplications
Considering the following integer multiplication: u64 = u16 * u16 What on earth, one might wonder, is the problem with this? Well, due to C's unfortunately abstruse integer semantics, both u16's are implicitly converted to int before the multiplication, which cannot hold all possible values of a u16 * u16. Even worse, after overflow the intermediate result will be a negative number, which during the conversion to a u64 will be sign-extended to a huge integer. Not good. The solution is to manually cast one of the u16 to a u32 or u64, which are large enough to not have any overflow and will prevent the implicit conversion. The type of the u64 is preferred, though a u32 is used instead of size_t, since that can change depending on the platform. Change-Id: I5391221d46d620d0e5bd629e2f9680be7a53342e Signed-off-by: Jacob Garber <jgarber1@ualberta.ca> Found-by: Coverity CID 12297{03,04,05,06,07,08,09,10} Reviewed-on: https://review.coreboot.org/c/coreboot/+/33986 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Julius Werner <jwerner@chromium.org> Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
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