This is a note to let you know that I've just added the patch titled
perf/core: Fix unconditional security_locked_down() call
to the 5.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-core-fix-unconditional-security_locked_down-call.patch
and it can be found in the queue-5.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 08ef1af4de5fe7de9c6d69f1e22e51b66e385d9b Mon Sep 17 00:00:00 2001
From: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
Date: Wed, 24 Feb 2021 22:56:28 +0100
Subject: perf/core: Fix unconditional security_locked_down() call
From: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
commit 08ef1af4de5fe7de9c6d69f1e22e51b66e385d9b upstream.
Currently, the lockdown state is queried unconditionally, even though
its result is used only if the PERF_SAMPLE_REGS_INTR bit is set in
attr.sample_type. While that doesn't matter in case of the Lockdown LSM,
it causes trouble with the SELinux's lockdown hook implementation.
SELinux implements the locked_down hook with a check whether the current
task's type has the corresponding "lockdown" class permission
("integrity" or "confidentiality") allowed in the policy. This means
that calling the hook when the access control decision would be ignored
generates a bogus permission check and audit record.
Fix this by checking sample_type first and only calling the hook when
its result would be honored.
Fixes: b0c8fdc7fdb7 ("lockdown: Lock down perf when in confidentiality mode")
Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20210224215628.192519-1-omosnace@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/events/core.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11829,12 +11829,12 @@ SYSCALL_DEFINE5(perf_event_open,
return err;
}
- err = security_locked_down(LOCKDOWN_PERF);
- if (err && (attr.sample_type & PERF_SAMPLE_REGS_INTR))
- /* REGS_INTR can leak data, lockdown must prevent this */
- return err;
-
- err = 0;
+ /* REGS_INTR can leak data, lockdown must prevent this */
+ if (attr.sample_type & PERF_SAMPLE_REGS_INTR) {
+ err = security_locked_down(LOCKDOWN_PERF);
+ if (err)
+ return err;
+ }
/*
* In cgroup mode, the pid argument is used to pass the fd
Patches currently in stable-queue which might be from omosnace@xxxxxxxxxx are
queue-5.12/perf-core-fix-unconditional-security_locked_down-call.patch
