Date: Wed, 28 May 2014 18:31:56 -0700 From: Andy Lutomirski <luto@...capital.net> To: Steve Grubb <sgrubb@...hat.com> Cc: oss-security@...ts.openwall.com Subject: Re: CVE request: Linux kernel DoS with syscall auditing On Wed, May 28, 2014 at 6:06 PM, Steve Grubb <sgrubb@...hat.com> wrote: > On Wednesday, May 28, 2014 02:45:59 PM Andy Lutomirski wrote: >> Issuing a system call with a random large number will OOPS, depending >> on configuration. A configuration that will enable this bug is: >> >> # auditctl -a exit,always -S open >> >> No privilege whatsoever is required to trigger the OOPS. > > Do you have more information about this? I don't get an oops and I run with > the audit system on all the time. It's on lkml -- see: http://thread.gmane.org/gmane.linux.kernel/1713178/focus=1713179 http://thread.gmane.org/gmane.linux.kernel/1712799/focus=1713161 You need to pass a fairly large bogus syscall number. The auditsc code is completely missing any bounds checking on the syscall numbers. > > >> It's possible that this can be extended to more than just a DoS -- >> with some care and willingness to exploit timing attacks, this is a >> read of arbitrary single bits in kernel memory. > > What platform? Where do the arbitrary bits go? What syscall are we talking > about? The audit system decides whether to log a syscall depending on a bit in the audit_krule mask. Since the mask read isn't bounds-checked, the caller can force it to read any bit, relative to the audit_krule. Anything that can tell the attacker the outcome of the filter decision will reveal the value of that bit. > > There is a linux-audit mail list which seems to not have any emails about this > problem. That is really the best place to discuss any issues with this > subsystem and get it fixed. There's already a patch on lkml. I'll cc linux-audit for the v2 patches. --Andy
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