Messages in this thread | | | Date | Sat, 22 Apr 2023 12:45:14 +0300 | From | Alexey Dobriyan <> | Subject | Re: [PATCH] ELF: use __builtin_mul_overflow() more |
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On Fri, Apr 21, 2023 at 12:39:11PM -0700, Andrew Morton wrote: > On Fri, 21 Apr 2023 21:54:36 +0300 Alexey Dobriyan <adobriyan@gmail.com> wrote: > > > __builtin_mul_overflow() can do multiplication and overflow check > > in one line. > > > > --- a/fs/binfmt_elf.c > > +++ b/fs/binfmt_elf.c > > @@ -1651,9 +1651,8 @@ static int fill_files_note(struct memelfnote *note, struct coredump_params *cprm > > > > /* *Estimated* file count and total data size needed */ > > count = cprm->vma_count; > > - if (count > UINT_MAX / 64) > > + if (__builtin_mul_overflow(count, 64, &size)) > > return -EINVAL; > > - size = count * 64; > > Huh, what the heck is that ;) > > > include/linux/overflow.h has check_mul_overflow() for us to use here.
Oh, no, wrappers.
> tools/lib/bpf/libbpf_internal.h uses > > #if __has_builtin(__builtin_mul_overflow) > > but check_mul_overflow() didn't bother testing for availability.
gcc 5.1 has __builtin_mul_overflow()
> Probably tools/lib/bpf/libbpf_internal.h should just use > check_mul_overflow().
I don't know, this is userspace stuff.
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