Date: Sat, 29 Dec 2012 16:52:49 +0400 From: Michael Tokarev <mjt@....msk.ru> To: oss-security@...ts.openwall.com Subject: Re: CVE request: qemu e1000 emulated device gues-side buffer overflow I'm not sure what's going on, but no one replied to this email. Meanwhile, this very place received one more bugfix -- see http://lists.nongnu.org/archive/html/qemu-devel/2012-12/msg00533.html Is this an issue serious enough to get a CVE#? Thanks, /mjt 19.12.2012 23:52, Michael Tokarev wrote: > qemu-1.3 includes the following patch by Michael Contreras: > > http://thread.gmane.org/gmane.comp.emulators.qemu/182666 > (initial submission) > http://git.qemu.org/?p=qemu.git;a=commitdiff;h=b0d9ffcd0251161c7c92f94804dcf599dfa3edeb > (the commit) > > > commit b0d9ffcd0251161c7c92f94804dcf599dfa3edeb > Author: Michael Contreras <michael@...tric.com> > Date: Sun Dec 2 20:11:22 2012 -0800 > Subject: e1000: Discard packets that are too long if !SBP and !LPE > > The e1000_receive function for the e1000 needs to discard packets longer than > 1522 bytes if the SBP and LPE flags are disabled. The linux driver assumes > this behavior and allocates memory based on this assumption. > > Signed-off-by: Michael Contreras <michael <at> inetric.com> > --- > > Tested with linux guest. This error can potentially be exploited. At the very > least it can cause a DoS to a guest system, and in the worse case it could > allow remote code execution on the guest system with kernel level privilege. > Risk seems low, as the network would need to be configured to allow large > packets. > > > The last comment, which didn't went into the commit message, indicates > that it is possible to send larger packet to a guest and cause a buffer > overflow with usual outcome in such cases. > > Yes indeed, the impact is rather low, because the network should be > configured to allow larger packets to reach the guest, which is not > usually the case -- either the host network is configure for MTU=1500 > and disallow large packets entirely, or BOTH host and guest network is > configured to allow large packets. In other words, either all devices > on the network are configred to accept jumbo frames, no no jumbo frames > are enabled at all. > > That's why I'm not sure whenever this can be considered a vulnerability > which deserves a CVE# or not, so I'm asking here. > > There's another followup bugfix in the same area, now talking about > "extra-large" frames -- > > http://thread.gmane.org/gmane.comp.emulators.qemu/183137 > > If this issue deserves a CVE#, I guess both patches can be seen as a > single bugfix. > > This impacts qemu and all products based on it and using e1000 emulated > device, including qemu-kvm, xen and others. > > Thanks, > > /mjt >
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