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Date: Fri, 17 Feb 2012 12:08:10 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/2] pci: rewrite devaddr parsing
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To: Eric Blake <eblake@redhat.com>
Cc: qemu-devel@nongnu.org

On Thu, Feb 16, 2012 at 01:39:02PM -0700, Eric Blake wrote:
> On 02/16/2012 12:23 PM, malc wrote:
> > On Thu, 16 Feb 2012, Michael S. Tsirkin wrote:
> > 
> >> Use scanf instead of manual string scanning.
> >>
> >> +
> >> +    /* Parse [[<domain>:]<bus>:]<slot> */
> >> +    sscanf(addr, "%x:%x:%x%n", &dom, &bus, &slot, &n);
> > 
> > sscanf can fail.
> 
> Worse, the *scanf family has undefined behavior on integer overflow.  If
> addr contains "100000000000000:0:0", there's no telling whether it will
> be diagnosed as a parse error, or silently accepted and truncated, in
> which case, there's no telling what dom will contain.
> 
> I cringe any time I see someone using scanf to parse numbers from
> arbitrary user input; I barely tolerate it for parsing things generated
> by the kernel, but even there, I won't ever use scanf myself.
> Same goes
> for atoi.  _Only_ strtol and friends can robustly parse arbitrary input
> into integers.

Seems easy to fix: I'll just set maximum field width of 8.
Any other issues?


> -- 
> Eric Blake   eblake@redhat.com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>