linux-kernel - Re: [PATCH -v2] Audit: push audit success and retcode into arch ptrace.h

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Date:	Wed, 8 Jun 2011 21:19:10 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Eric Paris <eparis@...hat.com>
Cc:	linux-kernel@...r.kernel.org, tony.luck@...el.com,
	fenghua.yu@...el.com, monstr@...str.eu, ralf@...ux-mips.org,
	benh@...nel.crashing.org, paulus@...ba.org, schwidefsky@...ibm.com,
	heiko.carstens@...ibm.com, linux390@...ibm.com,
	lethal@...ux-sh.org, davem@...emloft.net, jdike@...toit.com,
	richard@....at, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, viro@...iv.linux.org.uk,
	akpm@...ux-foundation.org, linux-ia64@...r.kernel.org,
	microblaze-uclinux@...e.uq.edu.au, linux-mips@...ux-mips.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [PATCH -v2] Audit: push audit success and retcode into arch
	ptrace.h

On 06/08, Oleg Nesterov wrote:
>
> OK. Thanks a lot Eric for your explanations.

Yes. but may I ask another one?

Shouldn't copy_process()->audit_alloc(tsk) path do
clear_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT) if it doesn't
set tsk->audit_context?

I can be easily wrong, but afaics otherwise the child can run
with TIF_SYSCALL_AUDIT bit copied from parent's thread_info by
dup_task_struct()->setup_thread_stack() and without ->audit_context,
right? For what?

Any other reason why audit_syscall_entry() checks context != NULL?

IOW. Any reason the patch below is wrong?

I am just curious, thanks.

Oleg.

--- x/kernel/auditsc.c
+++ x/kernel/auditsc.c
@@ -885,6 +885,8 @@ int audit_alloc(struct task_struct *tsk)
 	if (likely(!audit_ever_enabled))
 		return 0; /* Return if not auditing. */
 
+	clear_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
+
 	state = audit_filter_task(tsk, &key);
 	if (likely(state == AUDIT_DISABLED))
 		return 0;
@@ -1591,9 +1593,7 @@ void audit_syscall_entry(int arch, int m
 	struct audit_context *context = tsk->audit_context;
 	enum audit_state     state;
 
-	if (unlikely(!context))
-		return;
-
+	BUG_ON(!context);
 	/*
 	 * This happens only on certain architectures that make system
 	 * calls in kernel_thread via the entry.S interface, instead of

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