syslog: check cap_syslog when dmesg_restrict
Eric Paris pointed out that it doesn't make sense to require
both CAP_SYS_ADMIN and CAP_SYSLOG for certain syslog actions.
So require CAP_SYSLOG, not CAP_SYS_ADMIN, when dmesg_restrict
is set.
(I'm also consolidating the now common error path)
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: Kees Cook <kees.cook@canonical.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 209e158..5740671 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -219,7 +219,7 @@
This toggle indicates whether unprivileged users are prevented from using
dmesg(8) to view messages from the kernel's log buffer. When
dmesg_restrict is set to (0) there are no restrictions. When
-dmesg_restrict is set set to (1), users must have CAP_SYS_ADMIN to use
+dmesg_restrict is set set to (1), users must have CAP_SYSLOG to use
dmesg(8).
The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the default
diff --git a/kernel/printk.c b/kernel/printk.c
index 0712380..0cecba0 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -279,18 +279,12 @@
* at open time.
*/
if (type == SYSLOG_ACTION_OPEN || !from_file) {
- if (dmesg_restrict && !capable(CAP_SYS_ADMIN))
- return -EPERM;
+ if (dmesg_restrict && !capable(CAP_SYSLOG))
+ goto warn; /* switch to return -EPERM after 2.6.39 */
if ((type != SYSLOG_ACTION_READ_ALL &&
type != SYSLOG_ACTION_SIZE_BUFFER) &&
- !capable(CAP_SYSLOG)) {
- /* remove after 2.6.38 */
- if (capable(CAP_SYS_ADMIN))
- WARN_ONCE(1, "Attempt to access syslog with "
- "CAP_SYS_ADMIN but no CAP_SYSLOG "
- "(deprecated and denied).\n");
- return -EPERM;
- }
+ !capable(CAP_SYSLOG))
+ goto warn; /* switch to return -EPERM after 2.6.39 */
}
error = security_syslog(type);
@@ -434,6 +428,12 @@
}
out:
return error;
+warn:
+ /* remove after 2.6.39 */
+ if (capable(CAP_SYS_ADMIN))
+ WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN "
+ "but no CAP_SYSLOG (deprecated and denied).\n");
+ return -EPERM;
}
SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)