linux-kernel - [PATCH] integrity: get comm using lock to avoid race in string printing

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Message-Id: <11db0d126ef0ec7506ef5cb6f2f21c926d206436.1396455228.git.rgb@redhat.com>
Date:	Wed,  2 Apr 2014 12:19:51 -0400
From:	Richard Guy Briggs <rgb@...hat.com>
To:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org
Cc:	Richard Guy Briggs <rgb@...hat.com>, eparis@...hat.com,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>, sgrubb@...hat.com
Subject: [PATCH] integrity: get comm using lock to avoid race in string printing

When task->comm is passed directly to audit_log_untrustedstring() without
getting a copy or using the task_lock, there is a race that could happen that
would output a NULL (\0) in the output string that would effectively truncate
the rest of the report text after the comm= field in the audit, losing fields.

Use get_task_comm() to get a copy while acquiring the task_lock to prevent
this and to prevent the result from being a mixture of old and new values of
comm.

Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
---
 security/integrity/integrity_audit.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/security/integrity/integrity_audit.c b/security/integrity/integrity_audit.c
index 85253b5..11706a2 100644
--- a/security/integrity/integrity_audit.c
+++ b/security/integrity/integrity_audit.c
@@ -33,6 +33,7 @@ void integrity_audit_msg(int audit_msgno, struct inode *inode,
 			 const char *cause, int result, int audit_info)
 {
 	struct audit_buffer *ab;
+	char comm[sizeof(current->comm)];
 
 	if (!integrity_audit_info && audit_info == 1)	/* Skip info messages */
 		return;
@@ -49,7 +50,7 @@ void integrity_audit_msg(int audit_msgno, struct inode *inode,
 	audit_log_format(ab, " cause=");
 	audit_log_string(ab, cause);
 	audit_log_format(ab, " comm=");
-	audit_log_untrustedstring(ab, current->comm);
+	audit_log_untrustedstring(ab, get_task_comm(comm, current));
 	if (fname) {
 		audit_log_format(ab, " name=");
 		audit_log_untrustedstring(ab, fname);
-- 
1.7.1

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