Date: Wed, 19 Dec 2012 23:52:31 +0400 From: Michael Tokarev <mjt@....msk.ru> To: oss-security@...ts.openwall.com Subject: CVE request: qemu e1000 emulated device gues-side buffer overflow 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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