[PATCH 1/3] libdw: Make srclines use a stable sort

Josh Stone jistone at redhat.com
Mon Dec 15 21:48:28 UTC 2014

On 12/13/2014 03:18 PM, Mark Wielaard wrote:
> On Thu, Dec 11, 2014 at 05:34:06PM -0800, Josh Stone wrote:
>> BTW, I want to point out this change in compare_lines:
>>> -  return (*p1)->addr - (*p2)->addr;
>> [...]
>>> +  if (line1->addr != line2->addr)
>>> +    return (line1->addr < line2->addr) ? -1 : 1;
>> Since addr is 64-bit unsigned, and comparison functions return int, it
>> is possible for the difference to be so large that it wraps around.  You
>> only need INT_MAX or more -- which probably doesn't happen often in ELF
>> files, but it's plausible.
>> It might be worth auditing other qsort/tsearch comparison functions for
>> similar wrapping possibilities.
> I think you are right. I looked over all compare functions and two didn't
> do as you suggest. The attached patch fixes those. Do that look correct?

Those look good.

I think src/elfcmp.c compare_Elf32_Word() is also wrong, as big u32
values could wrap int subtraction.  I didn't find any others.


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