KEYS: Fix race between key destruction and finding a keyring by name

debian/changelog

@@ -1,3 +1,9 @@
+linux (4.2.3-3) UNRELEASED; urgency=medium
+
+  * KEYS: Fix race between key destruction and finding a keyring by name
+
+ -- Salvatore Bonaccorso <carnil@debian.org>  Mon, 19 Oct 2015 21:23:18 +0200
+
 linux (4.2.3-2) unstable; urgency=medium
 
   * nbd: Restore request timeout detection (Closes: #770479)

debian/patches/bugfix/all/0001-KEYS-Fix-race-between-key-destruction-and-finding-a-.patch

@@ -0,0 +1,52 @@
+From: David Howells <dhowells@redhat.com>
+Date: Fri, 25 Sep 2015 16:30:08 +0100
+Subject: KEYS: Fix race between key destruction and finding a keyring by name
+Origin: https://git.kernel.org/linus/94c4554ba07adbdde396748ee7ae01e86cf2d8d7
+
+There appears to be a race between:
+
+ (1) key_gc_unused_keys() which frees key->security and then calls
+     keyring_destroy() to unlink the name from the name list
+
+ (2) find_keyring_by_name() which calls key_permission(), thus accessing
+     key->security, on a key before checking to see whether the key usage is 0
+     (ie. the key is dead and might be cleaned up).
+
+Fix this by calling ->destroy() before cleaning up the core key data -
+including key->security.
+
+Reported-by: Petr Matousek <pmatouse@redhat.com>
+Signed-off-by: David Howells <dhowells@redhat.com>
+---
+ security/keys/gc.c | 8 ++++----
+ 1 file changed, 4 insertions(+), 4 deletions(-)
+
+diff --git a/security/keys/gc.c b/security/keys/gc.c
+index c795237..39eac1f 100644
+--- a/security/keys/gc.c
++++ b/security/keys/gc.c
+@@ -134,6 +134,10 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
+ 		kdebug("- %u", key->serial);
+ 		key_check(key);
+ 
++		/* Throw away the key data */
++		if (key->type->destroy)
++			key->type->destroy(key);
++
+ 		security_key_free(key);
+ 
+ 		/* deal with the user's key tracking and quota */
+@@ -148,10 +152,6 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
+ 		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
+ 			atomic_dec(&key->user->nikeys);
+ 
+-		/* now throw away the key memory */
+-		if (key->type->destroy)
+-			key->type->destroy(key);
+-
+ 		key_user_put(key->user);
+ 
+ 		kfree(key->description);
+-- 
+2.6.1
+

debian/patches/series

@@ -107,3 +107,5 @@ bugfix/x86/crypto-x86-camellia_aesni_avx-fix-cpu-feature-checks.patch
 bugfix/all/nbd-fix-timeout-detection.patch
 bugfix/all/nbd-remove-variable-pid.patch
 bugfix/all/nbd-add-locking-for-tasks.patch
+
+bugfix/all/0001-KEYS-Fix-race-between-key-destruction-and-finding-a-.patch