Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966535AbcCPIUD (ORCPT ); Wed, 16 Mar 2016 04:20:03 -0400 Received: from mail.kernel.org ([198.145.29.136]:60497 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966418AbcCPIMU (ORCPT ); Wed, 16 Mar 2016 04:12:20 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, David Howells , Zefan Li Subject: [PATCH 3.4 085/107] KEYS: Fix race between key destruction and finding a keyring by name Date: Wed, 16 Mar 2016 16:06:19 +0800 Message-Id: <1458115601-5762-85-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1458115541-5712-1-git-send-email-lizf@kernel.org> References: <1458115541-5712-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1674 Lines: 57 From: David Howells 3.4.111-rc1 review patch. If anyone has any objections, please let me know. ------------------ 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 --- 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 87632bd..f85d638 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); -- 1.9.1