From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966323AbaFQVtF (ORCPT ); Tue, 17 Jun 2014 17:49:05 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:54109 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966283AbaFQVtA (ORCPT ); Tue, 17 Jun 2014 17:49:00 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Darren Hart , Kees Cook , Will Drewry , Thomas Gleixner , Linus Torvalds , Kamal Mostafa Subject: [PATCH 3.13 207/212] futex: Validate atomic acquisition in futex_lock_pi_atomic() Date: Tue, 17 Jun 2014 14:45:01 -0700 Message-Id: <1403041506-13646-208-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1403041506-13646-1-git-send-email-kamal@canonical.com> References: <1403041506-13646-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11.4 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner commit b3eaa9fc5cd0a4d74b18f6b8dc617aeaf1873270 upstream. We need to protect the atomic acquisition in the kernel against rogue user space which sets the user space futex to 0, so the kernel side acquisition succeeds while there is existing state in the kernel associated to the real owner. Verify whether the futex has waiters associated with kernel state. If it has, return -EINVAL. The state is corrupted already, so no point in cleaning it up. Subsequent calls will fail as well. Not our problem. [ tglx: Use futex_top_waiter() and explain why we do not need to try restoring the already corrupted user space state. ] Signed-off-by: Darren Hart Cc: Kees Cook Cc: Will Drewry Signed-off-by: Thomas Gleixner Signed-off-by: Linus Torvalds Signed-off-by: Kamal Mostafa --- kernel/futex.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index c861191..9c6b0e1 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -764,10 +764,18 @@ retry: return -EDEADLK; /* - * Surprise - we got the lock. Just return to userspace: + * Surprise - we got the lock, but we do not trust user space at all. */ - if (unlikely(!curval)) - return 1; + if (unlikely(!curval)) { + /* + * We verify whether there is kernel state for this + * futex. If not, we can safely assume, that the 0 -> + * TID transition is correct. If state exists, we do + * not bother to fixup the user space state as it was + * corrupted already. + */ + return futex_top_waiter(hb, key) ? -EINVAL : 1; + } uval = curval; -- 1.9.1