Date: Fri, 27 Jul 2018 08:07:13 -0400 From: Jordan Glover <Golden_Miller83@...tonmail.ch> To: Steven Rostedt <rostedt@...dmis.org> Cc: Nick Desaulniers <ndesaulniers@...gle.com>, "greg@...ah.com" <greg@...ah.com>, Kees Cook <keescook@...gle.com>, "salyzyn@...roid.com" <salyzyn@...roid.com>, LKML <linux-kernel@...r.kernel.org>, "mingo@...hat.com" <mingo@...hat.com>, "kernel-team@...roid.com" <kernel-team@...roid.com>, "stable@...r.kernel.org" <stable@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH] tracing: do not leak kernel addresses On July 27, 2018 12:15 AM, Steven Rostedt <rostedt@...dmis.org> wrote: > On Thu, 26 Jul 2018 09:52:11 -0700 > Nick Desaulniers ndesaulniers@...gle.com wrote: > > > See the section "Kernel addresses" in > > Documentation/security/self-protection. IIRC, the issue is that a > > process may have CAP_SYSLOG but not necessarily CAP_SYS_ADMIN (so it > > can read dmesg, but not necessarily issue a sysctl to change > > kptr_restrict), get compromised and used to leak kernel addresses, > > which can then be used to defeat KASLR. > > But the code doesn't go to dmesg. It's only available > via /sys/kernel/debug/tracing/printk_formats which is only available > via root. Nobody else has access to that directory. > > -- Steve I think the point was that when we take capabilities into account the root privileges aren't unequivocal anymore. The 'root' owned process with only 'CAP_SYSLOG' shouldn't have access to /sys/kernel/debug/tracing/printk_formats Jordan
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