Kees Cook <keescook at chromium.org> writes: > On Tue, May 9, 2017 at 4:13 PM, Daniel Micay <danielmicay at gmail.com> wrote: >> On Tue, 2017-05-09 at 16:06 -0700, Kees Cook wrote: >>> Defining kexec_purgatory as a zero-length char array upsets compile >>> time size checking. Since this is entirely runtime sized, switch >>> this to void *. This silences the warning generated by the future >>> CONFIG_FORTIFY_SOURCE, which did not like the memcmp() of a "0 byte" >>> array. >>> >>> Cc: Daniel Micay <danielmicay at gmail.com> >>> Signed-off-by: Kees Cook <keescook at chromium.org> >>> --- >>> kernel/kexec_file.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c >>> index b118735fea9d..bc86f85f1329 100644 >>> --- a/kernel/kexec_file.c >>> +++ b/kernel/kexec_file.c >>> @@ -30,7 +30,7 @@ >>> * Declare these symbols weak so that if architecture provides a >>> purgatory, >>> * these will be overridden. >>> */ >>> -char __weak kexec_purgatory[0]; >>> +void * __weak kexec_purgatory; >>> size_t __weak kexec_purgatory_size = 0; >>> >>> static int kexec_calculate_store_digests(struct kimage *image); >>> -- >>> 2.7.4 >> >> It seems more correct to use char `char __weak kexec_purgatory[]`, >> otherwise isn't __builtin_object_size ending up as 8, which is still >> wrong? > > I tried [], that was my instinct, too, but since this is a __weak and > not an extern, that doesn't work: > > kernel/kexec_file.c:33:13: warning: array ?kexec_purgatory? assumed to > have one element > char __weak kexec_purgatory[]; > ^~~~~~~~~~~~~~~ Nor does "void *kexec_purgatory" as that says at the address known as kexec_purgatory is a void pointer not a blob a bytes that can be used for something interesting. Better to get rid of the __weak and deal with that fallout. Eric
