Re: [PATCH] strings: Produce error when section data falls outside file.

[Mark Wielaard <mark at klomp dot org>]

On Sat, Dec 27, 2014 at 04:31:14AM +0300, Alexander Cherepanov wrote:
> On 2014-12-27 01:00, Mark Wielaard wrote:
> >diff --git a/src/strings.c b/src/strings.c
> >index f60e4b4..d1eb7b2 100644
> >--- a/src/strings.c
> >+++ b/src/strings.c
> >@@ -725,8 +725,21 @@ read_elf (Elf *elf, int fd, const char *fname, off64_t fdlen)
> >  	 actually have content.  */
> >        if (shdr != NULL && shdr->sh_type != SHT_NOBITS
> >  	  && (shdr->sh_flags & SHF_ALLOC) != 0)
> >-	result |= read_block (fd, fname, fdlen, shdr->sh_offset,
> >-			      shdr->sh_offset + shdr->sh_size);
> >+	{
> >+	  if (shdr->sh_offset > fdlen
> >+	      || fdlen - shdr->sh_offset < shdr->sh_size)
> >+	    {
> 
> It fails to build for me:
> 
> strings.c: In function 'read_elf':
> strings.c:729:24: error: comparison between signed and unsigned integer
> expressions [-Werror=sign-compare]
>     if (shdr->sh_offset > fdlen

The compiler is correct. sh_offset is an unsigned Elf64_Off and fdlen is
a signed off64_t. But just before we already checked fdlen >= 0, so we
can just cast it to Elf64_Off safely for this comparison. As attached.

Thanks,

Mark

Attachment: 0001-strings-Produce-error-when-section-data-falls-outsid.patch
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