On July 27, 2018 12:15 AM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > On Thu, 26 Jul 2018 09:52:11 -0700 > Nick Desaulniers ndesaulniers@xxxxxxxxxx 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
