Date: Wed, 26 Sep 2012 12:43:19 -0400 From: Tom Lane <tgl@...hat.com> To: Huzaifa Sidhpurwala <huzaifas@...hat.com> cc: Sebastian Krahmer <krahmer@...e.de>, oss-security@...ts.openwall.com Subject: Re: CVE Request: libtiff: Heap-buffer overflow when processing a TIFF image with PixarLog Compression Huzaifa Sidhpurwala <huzaifas@...hat.com> writes: > On 09/26/2012 12:27 PM, Sebastian Krahmer wrote: >> As well as the patch: >> >> >> - sp->tbuf = (uint16 *) _TIFFmalloc(tbuf_size); >> + sp->tbuf = (uint16 *) _TIFFmalloc(tbuf_size+sizeof(uint16)*sp->stride); >> >> If there were sizeof(uint16)*sp->stride bytes missing before, this is really >> more than just a few bytes. I checked that the mult cannot overflow, >> as sp->stride seems to be uint16. However, I think the add can actually wrap, >> (at least on ILP32) as tbuf_size can be 0xffffffff or so. >> I think the patch is broken and just shifts the hole. >> > It seems that sp->stride is at most td_samplesperpixel. > Re-thinking about the patch, it does seem a bit broken now. > Tom, > Any inputs on this? Yeah, I was wondering about the possibility of an overflow there too. The amount being added is very small but in principle tbuf_size could be just below the overflow threshold. And I agree that it would be saner to increase tbuf_size itself. Having said all that, I still don't understand why this buffer needs padding at all. regards, tom lane
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