Messages in this thread | | | Date | Mon, 11 Mar 2019 20:10:06 +0300 | From | Alexey Dobriyan <> | Subject | Re: [PATCH 1/4] elf: don't be afraid of overflow |
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On Mon, Mar 11, 2019 at 12:04:23PM +0100, Pavel Machek wrote: > On Mon 2019-02-04 23:27:15, Alexey Dobriyan wrote: > > Number of ELF program headers is 16-bit by spec, so total size > > comfortably fits into "unsigned int". > > If it can't overflow, gcc should know too, and optimize checks > out... right?
Turns out it doesn't.
> > @@ -429,13 +430,9 @@ static struct elf_phdr *load_elf_phdrs(struct elfhdr *elf_ex, > > goto out; > > > > /* Sanity check the number of program headers... */ > > - if (elf_ex->e_phnum < 1 || > > - elf_ex->e_phnum > 65536U / sizeof(struct elf_phdr)) > > - goto out; > > - > > /* ...and their total size. */ > > This is just wrong. You removed check for zero, and I'm pretty sure > sizeof() is not 1, so this one can trigger, too.
No. ->e_phnum is 65535 max.
size = sizeof(struct elf_phdr) * elf_ex->e_phnum; if (size == 0 || size > 65536 || size > ELF_MIN_ALIGN) goto out;
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