kernel: fix keyring reference leak (CVE-2016-0728)

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Backport of r48372

SVN-Revision: 48373

diff --git a/target/linux/generic/patches-3.18/010-KEYS-Fix-keyring-ref-leak-in-join_session_keyring.patch b/target/linux/generic/patches-3.18/010-KEYS-Fix-keyring-ref-leak-in-join_session_keyring.patch
new file mode 100644 (file)
index 0000000..9c6a969
--- /dev/null
+++ b/target/linux/generic/patches-3.18/010-KEYS-Fix-keyring-ref-leak-in-join_session_keyring.patch
@@ -0,0 +1,75 @@
+From 7ca88764d45c209791e8813131c1457c2e9e51e7 Mon Sep 17 00:00:00 2001
+From: Yevgeny Pats <yevgeny@perception-point.io>
+Date: Mon, 11 Jan 2016 12:05:28 +0000
+Subject: KEYS: Fix keyring ref leak in join_session_keyring()
+
+If a thread is asked to join as a session keyring the keyring that's already
+set as its session, we leak a keyring reference.
+
+This can be tested with the following program:
+
+       #include <stddef.h>
+       #include <stdio.h>
+       #include <sys/types.h>
+       #include <keyutils.h>
+
+       int main(int argc, const char *argv[])
+       {
+               int i = 0;
+               key_serial_t serial;
+
+               serial = keyctl(KEYCTL_JOIN_SESSION_KEYRING,
+                               "leaked-keyring");
+               if (serial < 0) {
+                       perror("keyctl");
+                       return -1;
+               }
+
+               if (keyctl(KEYCTL_SETPERM, serial,
+                          KEY_POS_ALL | KEY_USR_ALL) < 0) {
+                       perror("keyctl");
+                       return -1;
+               }
+
+               for (i = 0; i < 100; i++) {
+                       serial = keyctl(KEYCTL_JOIN_SESSION_KEYRING,
+                                       "leaked-keyring");
+                       if (serial < 0) {
+                               perror("keyctl");
+                               return -1;
+                       }
+               }
+
+               return 0;
+       }
+
+If, after the program has run, there something like the following line in
+/proc/keys:
+
+3f3d898f I--Q---   100 perm 3f3f0000     0     0 keyring   leaked-keyring: empty
+
+with a usage count of 100 * the number of times the program has been run,
+then the kernel is malfunctioning.  If leaked-keyring has zero usages or
+has been garbage collected, then the problem is fixed.
+
+Reported-by: Yevgeny Pats <yevgeny@perception-point.io>
+Signed-off-by: David Howells <dhowells@redhat.com>
+---
+ security/keys/process_keys.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
+index a3f85d2..e6d50172 100644
+--- a/security/keys/process_keys.c
++++ b/security/keys/process_keys.c
+@@ -794,6 +794,7 @@ long join_session_keyring(const char *name)
+               ret = PTR_ERR(keyring);
+               goto error2;
+       } else if (keyring == new->session_keyring) {
++              key_put(keyring);
+               ret = 0;
+               goto error2;
+       }
+-- 
+2.7.0.rc3
+