On Tue, Oct 12, 2021 at 06:29:53PM +1100, Daniel Axtens wrote: > grub_mm_region_init() does: > > h = (grub_mm_header_t) (r + 1); > > where h is a grub_mm_header_t and r is a grub_mm_region_t. > > Cells are supposed to be GRUB_MM_ALIGN aligned, but while grub_mm_dump > ensures this vs the region header, grub_mm_region_init() does not. > > It's better to be explicit than implicit here: rather than changing > grub_mm_region_init() to ALIGN_UP(), require that the struct is > explictly a multiple of the header size. > > Signed-off-by: Daniel Axtens <d...@axtens.net> > --- > include/grub/mm_private.h | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/include/grub/mm_private.h b/include/grub/mm_private.h > index e80a059dd4e4..533b47173e18 100644 > --- a/include/grub/mm_private.h > +++ b/include/grub/mm_private.h > @@ -20,6 +20,7 @@ > #define GRUB_MM_PRIVATE_H 1 > > #include <grub/mm.h> > +#include <grub/misc.h> > > /* Magic words. */ > #define GRUB_MM_FREE_MAGIC 0x2d3c2808 > @@ -82,4 +83,11 @@ typedef struct grub_mm_region > extern grub_mm_region_t EXPORT_VAR (grub_mm_base); > #endif > > +static inline void grub_mm_size_sanity_check(void) {
static inline void grub_mm_size_sanity_check (void) { > + /* Ensure we preserve alignment when doing h = (grub_mm_header_t) (r + 1) > */ > + COMPILE_TIME_ASSERT((sizeof(struct grub_mm_region) % Missing spaces before "(" above and below... s/struct grub_mm_region/grub_mm_region_t/ s/struct grub_mm_header/grub_mm_header_t/ > + sizeof(struct grub_mm_header)) == 0); I think this check is insufficient. The GRUB_MM_ALIGN should be checked somehow too. E.g. if sizeof(struct grub_mm_region) == 16, sizeof(struct grub_mm_header) == 8 and GRUB_MM_ALIGN == 32 then assert above will pass but the GRUB will blow up later. Of course numbers are not real but I chose them to show the problem. Hmmm... If we could choose grub_mm_region_t and grub_mm_header_t sizes properly then probably we could drop GRUB_MM_ALIGN... Daniel _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel