On Mon, Jan 22 2024 at 7:27P -0500, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > In an effort to separate intentional arithmetic wrap-around from > unexpected wrap-around, we need to refactor places that depend on this > kind of math. One of the most common code patterns of this is: > > VAR + value < VAR > > Notably, this is considered "undefined behavior" for signed and pointer > types, which the kernel works around by using the -fno-strict-overflow > option in the build[1] (which used to just be -fwrapv). Regardless, we > want to get the kernel source to the position where we can meaningfully > instrument arithmetic wrap-around conditions and catch them when they > are unexpected, regardless of whether they are signed[2], unsigned[3], > or pointer[4] types. > > Refactor open-coded wrap-around addition test to use add_would_overflow(). > This paves the way to enabling the wrap-around sanitizers in the future. > > Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] > Link: https://github.com/KSPP/linux/issues/26 [2] > Link: https://github.com/KSPP/linux/issues/27 [3] > Link: https://github.com/KSPP/linux/issues/344 [4] > Cc: Alasdair Kergon <agk@xxxxxxxxxx> > Cc: Mike Snitzer <snitzer@xxxxxxxxxx> > Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx> > Cc: dm-devel@xxxxxxxxxxxxxxx > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Please change subject to: "dm: Refactor intentional wrap-around test in a few targets" Reviewed-by: Mike Snitzer <snitzer@xxxxxxxxxx>
