linux-kernel - Re: [PATCH] Change task

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Message-Id: <201403112102.HCC48418.LSOQFJOFOtFVHM@I-love.SAKURA.ne.jp>
Date:	Tue, 11 Mar 2014 21:02:40 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	rgb@...hat.com
Cc:	peterz@...radead.org, paulmck@...ux.vnet.ibm.com,
	laijs@...fujitsu.com, akpm@...ux-foundation.org, joe@...ches.com,
	keescook@...omium.org, geert@...ux-m68k.org, jkosina@...e.cz,
	viro@...iv.linux.org.uk, davem@...emloft.net,
	linux-kernel@...r.kernel.org, mingo@...e.hu, rostedt@...dmis.org,
	tglx@...utronix.de, linux-security-module@...r.kernel.org
Subject: Re: [PATCH] Change task_struct->comm to use RCU.

Richard Guy Briggs wrote:
> > Even if you don't trust the comm= field, it is annoying for me that fields
> > after comm= are missing in the audit log.
> 
> More than annoying, that isn't acceptable.
> 
OK. If you are sure that it is safe to use get_task_comm() from
audit_log_task() and you prefer locked version, please pick up below patch
via your git tree.

If you are unsure or prefer lockless version, I'll make a lockless version
using do_get_task_comm() proposed in this thread.

----------
>>From 88c3ff13efa10df6f4d4d0f2c243124ce6a3eaeb Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Date: Tue, 11 Mar 2014 20:47:29 +0900
Subject: [PATCH] Audit: Pass comm name via get_task_comm()

When we pass task->comm to audit_log_untrustedstring(), we need to pass
a snapshot of it using get_task_comm(). Otherwise, we will lose fields
after comm= if we raced with updating task->comm.

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
 kernel/auditsc.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 7aef2f4..ba57993 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2357,6 +2357,7 @@ static void audit_log_task(struct audit_buffer *ab)
 	kgid_t gid;
 	unsigned int sessionid;
 	struct mm_struct *mm = current->mm;
+	char name[TASK_COMM_LEN];
 
 	auid = audit_get_loginuid(current);
 	sessionid = audit_get_sessionid(current);
@@ -2369,7 +2370,7 @@ static void audit_log_task(struct audit_buffer *ab)
 			 sessionid);
 	audit_log_task_context(ab);
 	audit_log_format(ab, " pid=%d comm=", current->pid);
-	audit_log_untrustedstring(ab, current->comm);
+	audit_log_untrustedstring(ab, get_task_comm(name, current));
 	if (mm) {
 		down_read(&mm->mmap_sem);
 		if (mm->exe_file)
-- 
1.7.9.5
--
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