diff mbox

[3.13.y-ckt,128/132] security_syslog() should be called once only

Message ID 1437616850-23266-129-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa July 23, 2015, 2 a.m. UTC 
3.13.11-ckt24 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vasily Averin <vvs@virtuozzo.com>

commit d194e5d666225b04c7754471df0948f645b6ab3a upstream.

The final version of commit 637241a900cb ("kmsg: honor dmesg_restrict
sysctl on /dev/kmsg") lost few hooks, as result security_syslog() are
processed incorrectly:

- open of /dev/kmsg checks syslog access permissions by using
  check_syslog_permissions() where security_syslog() is not called if
  dmesg_restrict is set.

- syslog syscall and /proc/kmsg calls do_syslog() where security_syslog
  can be executed twice (inside check_syslog_permissions() and then
  directly in do_syslog())

With this patch security_syslog() is called once only in all
syslog-related operations regardless of dmesg_restrict value.

Fixes: 637241a900cb ("kmsg: honor dmesg_restrict sysctl on /dev/kmsg")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 kernel/printk/printk.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)
diff mbox

Patch

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 886555f..9b6f5d2 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -383,11 +383,11 @@  static int check_syslog_permissions(int type, bool from_file)
 	 * already done the capabilities checks at open time.
 	 */
 	if (from_file && type != SYSLOG_ACTION_OPEN)
-		return 0;
+		goto ok;
 
 	if (syslog_action_restricted(type)) {
 		if (capable(CAP_SYSLOG))
-			return 0;
+			goto ok;
 		/*
 		 * For historical reasons, accept CAP_SYS_ADMIN too, with
 		 * a warning.
@@ -397,10 +397,11 @@  static int check_syslog_permissions(int type, bool from_file)
 				     "CAP_SYS_ADMIN but no CAP_SYSLOG "
 				     "(deprecated).\n",
 				 current->comm, task_pid_nr(current));
-			return 0;
+			goto ok;
 		}
 		return -EPERM;
 	}
+ok:
 	return security_syslog(type);
 }
 
@@ -1130,10 +1131,6 @@  int do_syslog(int type, char __user *buf, int len, bool from_file)
 	if (error)
 		goto out;
 
-	error = security_syslog(type);
-	if (error)
-		return error;
-
 	switch (type) {
 	case SYSLOG_ACTION_CLOSE:	/* Close log */
 		break;