From: David Howells Date: Fri, 25 Sep 2015 15:30:08 +0000 (+0100) Subject: KEYS: Fix race between key destruction and finding a keyring by name X-Git-Tag: v3.4.111~23 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=48ec02cc771de41cc8b063a2f60890242c09bfba;p=thirdparty%2Fkernel%2Fstable.git KEYS: Fix race between key destruction and finding a keyring by name commit 94c4554ba07adbdde396748ee7ae01e86cf2d8d7 upstream. 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 Signed-off-by: David Howells [lizf: Backported to 3.4: adjust indentation] Signed-off-by: Zefan Li --- diff --git a/security/keys/gc.c b/security/keys/gc.c index 87632bd17b3e8..f85d6381c06ef 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -174,6 +174,10 @@ static noinline void key_gc_unused_key(struct key *key) { 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 */ @@ -188,10 +192,6 @@ static noinline void key_gc_unused_key(struct key *key) 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);