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perf/core: Change the default paranoia level to 2

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Allowing unprivileged kernel profiling lets any user dump follow kernel
control flow and dump kernel registers.  This most likely allows trivial
kASLR bypassing, and it may allow other mischief as well.  (Off the top
of my head, the PERF_SAMPLE_REGS_INTR output during /dev/urandom reads
could be quite interesting.)

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andy Lutomirski 2016-05-09 15:48:51 -07:00 • committed by Linus Torvalds
parent 5c56b563b4
commit 0161028b7c
2 changed files with 2 additions and 2 deletions
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2
Documentation/sysctl/kernel.txt
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@ -645,7 +645,7 @@ allowed to execute.
perf_event_paranoid: perf_event_paranoid:
Controls use of the performance events system by unprivileged Controls use of the performance events system by unprivileged
users (without CAP_SYS_ADMIN). The default value is 1. users (without CAP_SYS_ADMIN). The default value is 2.
-1: Allow use of (almost) all events by all users -1: Allow use of (almost) all events by all users
>=0: Disallow raw tracepoint access by users without CAP_IOC_LOCK >=0: Disallow raw tracepoint access by users without CAP_IOC_LOCK

2
kernel/events/core.c
View file

@ -351,7 +351,7 @@ static struct srcu_struct pmus_srcu;
* 1 - disallow cpu events for unpriv * 1 - disallow cpu events for unpriv
* 2 - disallow kernel profiling for unpriv * 2 - disallow kernel profiling for unpriv
*/ */
int sysctl_perf_event_paranoid __read_mostly = 1; int sysctl_perf_event_paranoid __read_mostly = 2;
/* Minimum for 512 kiB + 1 user control page */ /* Minimum for 512 kiB + 1 user control page */
int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */ int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */