linux-kernel - [PATCH 1/4] audit: Syscall rules are not applied to existing processes on non-x86

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Message-ID: <20130109104617.74e995a5@kryten>
Date:	Wed, 9 Jan 2013 10:46:17 +1100
From:	Anton Blanchard <anton@...ba.org>
To:	eparis@...hat.com, viro@...iv.linux.org.uk,
	benh@...nel.crashing.org, paulus@...ba.org
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 1/4] audit: Syscall rules are not applied to existing
 processes on non-x86

Commit b05d8447e782 (audit: inline audit_syscall_entry to reduce
burden on archs) changed audit_syscall_entry to check for a dummy
context before calling __audit_syscall_entry. Unfortunately the dummy
context state is maintained in __audit_syscall_entry so once set it
never gets cleared, even if the audit rules change.

As a result, if there are no auditing rules when a process starts
then it will never be subject to any rules added later. x86 doesn't
see this because it has an assembly fast path that calls directly into
__audit_syscall_entry.

I noticed this issue when working on audit performance optimisations.
I wrote a set of simple test cases available at:

http://ozlabs.org/~anton/junkcode/audit_tests.tar.gz

02_new_rule.py fails without the patch and passes with it. The
test case clears all rules, starts a process, adds a rule then
verifies the process produces a syscall audit record.

Signed-off-by: Anton Blanchard <anton@...ba.org>
Cc: <stable@...nel.org> # 3.3+
---

Index: b/include/linux/audit.h
===================================================================
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -119,7 +119,7 @@ static inline void audit_syscall_entry(i
 				       unsigned long a1, unsigned long a2,
 				       unsigned long a3)
 {
-	if (unlikely(!audit_dummy_context()))
+	if (unlikely(current->audit_context))
 		__audit_syscall_entry(arch, major, a0, a1, a2, a3);
 }
 static inline void audit_syscall_exit(void *pt_regs)
--
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