On 07/10/2020 00.02, Simon Glass wrote: > Hi Rasmus, > > On Tue, 6 Oct 2020 at 04:10, Rasmus Villemoes > <rasmus.villem...@prevas.dk> wrote: >> >> Commit fdf0819afb (rsa: fix alignment issue when getting public >> exponent) changed the logic to avoid doing an 8-byte access to a >> possibly-not-8-byte-aligned address. >> >> However, using rsa_convert_big_endian is wrong: That function converts >> an array of big-endian (32-bit) words with the most significant word >> first (aka a BE byte array) to an array of cpu-endian words with the >> least significant word first. While the exponent is indeed _stored_ as >> a big-endian 64-bit word (two BE words with MSW first), we want to >> extract it as a cpu-endian 64 bit word. On a little-endian host, >> swapping the words and byte-swapping each 32-bit word works, because >> that's the same as byte-swapping the whole 64 bit word. But on a >> big-endian host, the fdt32_to_cpu are no-ops, but >> rsa_convert_big_endian() still does the word-swapping, breaking >> verified boot. >> >> To fix that, while still ensuring we don't do unaligned accesses, add >> a little helper that first memcpy's the bytes to a local fdt64_t, then >> applies fdt64_to_cpu(). [The name is chosen based on the >> [bl]eXX_to_cpup in linux/byteorder/generic.h]. >> >> Fixes: fdf0819afb ("rsa: fix alignment issue when getting public exponent") >> Signed-off-by: Rasmus Villemoes <rasmus.villem...@prevas.dk> >> --- >> lib/rsa/rsa-mod-exp.c | 11 +++++++++-- >> 1 file changed, 9 insertions(+), 2 deletions(-) >> > > Reviewed-by: Simon Glass <s...@chromium.org> > > Is there a way to add a test for this?
Not that I can think of, other than finding some BE board and hooking it up in some CI. Apparently not very many people use verified boot on BE platforms :( or at least they don't follow upstream U-Boot closely. Rasmus