Date: Tue, 12 Apr 2011 15:22:22 +0400 From: Vasiliy Kulikov <segoon@...nwall.com> To: oss-security@...ts.openwall.com Cc: Moritz Muehlenhoff <jmm@...ian.org> Subject: Re: CVE requests: Three Linux kernel issues On Mon, Apr 11, 2011 at 18:54 -0400, Dan Rosenberg wrote: > Firstly, this driver has locking that only allows one open file > descriptor at once. Yes, but the process that opened the file may: 1) give fd to another process. 2) call fork(). And since de-BLK-ization 2+ processes may run read()/write() simultaneously. > Even if you can work around this, you'd have a race window of about > two instructions, with basically no possibility of being preempted > since there's no blocking or potentially faulting operation. And > that's assuming it's even possible, since it may be the case that this > index is in a register, which would render this completely > unexploitable. > > Assuming this isn't the case, and you're running an SMP system and > spent countless hours (days? weeks?) spinning to hit this extremely > narrow race, you then get to write a single byte past the end of this > array, into the vfd_is_open integer, which is already set to 1 (it's > treated as a boolean value). Agreed, I thought about it too :-) AFAIU, all these 3 drivers are not available to non-root users. -- Vasiliy Kulikov http://www.openwall.com - bringing security into open computing environments Download attachment "signature.asc" of type "application/pgp-signature" (837 bytes)
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