Commit d194e5d6 authored Jun 25, 2015 by Vasily Averin Committed by Linus Torvalds Jun 25, 2015

security_syslog() should be called once only



The final version of commit 637241a9 ("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: 637241a9 ("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>

parent e2f15f9a

kernel/printk/printk.c

+4 −7

Original line number	Diff line number	Diff line
		@@ -496,11 +496,11 @@ 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.
		@@ -510,10 +510,11 @@ 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);
		}

		@@ -1299,10 +1300,6 @@ 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;