linux-kernel - Re: [PATCH] Change task

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Message-Id: <201403112116.HIJ21362.OFVQJFtHOSOFLM@I-love.SAKURA.ne.jp>
Date:	Tue, 11 Mar 2014 21:16:44 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	jmorris@...ei.org
Cc:	rgb@...hat.com, 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.

And the same phrase goes to James Morris...

If you are sure that it is safe to use get_task_comm() from
dump_common_audit_data() 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 1fe3dcd8792bc1296e337daba661200a8feaf706 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Date: Tue, 11 Mar 2014 21:09:48 +0900
Subject: [PATCH] LSM: 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>
---
 security/lsm_audit.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/security/lsm_audit.c b/security/lsm_audit.c
index 9a62045..6291c67 100644
--- a/security/lsm_audit.c
+++ b/security/lsm_audit.c
@@ -212,6 +212,7 @@ static void dump_common_audit_data(struct audit_buffer *ab,
 				   struct common_audit_data *a)
 {
 	struct task_struct *tsk = current;
+	char name[TASK_COMM_LEN];
 
 	/*
 	 * To keep stack sizes in check force programers to notice if they
@@ -221,7 +222,7 @@ static void dump_common_audit_data(struct audit_buffer *ab,
 	BUILD_BUG_ON(sizeof(a->u) > sizeof(void *)*2);
 
 	audit_log_format(ab, " pid=%d comm=", tsk->pid);
-	audit_log_untrustedstring(ab, tsk->comm);
+	audit_log_untrustedstring(ab, get_task_comm(name, tsk));
 
 	switch (a->type) {
 	case LSM_AUDIT_DATA_NONE:
@@ -280,7 +281,7 @@ static void dump_common_audit_data(struct audit_buffer *ab,
 		tsk = a->u.tsk;
 		if (tsk && tsk->pid) {
 			audit_log_format(ab, " pid=%d comm=", tsk->pid);
-			audit_log_untrustedstring(ab, tsk->comm);
+			audit_log_untrustedstring(ab, get_task_comm(name, tsk));
 		}
 		break;
 	case LSM_AUDIT_DATA_NET:
-- 
1.7.9.5
--
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