Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753980Ab0LAC14 (ORCPT ); Tue, 30 Nov 2010 21:27:56 -0500 Received: from DMZ-MAILSEC-SCANNER-5.MIT.EDU ([18.7.68.34]:49825 "EHLO dmz-mailsec-scanner-5.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753622Ab0LAC1z (ORCPT ); Tue, 30 Nov 2010 21:27:55 -0500 X-AuditID: 12074422-b7c3eae000000a70-88-4cf5b2aad941 From: Nelson Elhage To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Nelson Elhage Subject: [PATCH v2] do_exit(): Make sure we run with get_fs() == USER_DS. Date: Tue, 30 Nov 2010 21:27:36 -0500 Message-Id: <1291170456-22580-1-git-send-email-nelhage@ksplice.com> X-Mailer: git-send-email 1.7.1.31.g6297e In-Reply-To: <20101130174947.5ccc3778.akpm@linux-foundation.org> References: <20101130174947.5ccc3778.akpm@linux-foundation.org> X-Brightmail-Tracker: AAAAARbTrbM= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1488 Lines: 41 If a user manages to trigger an oops with fs set to KERNEL_DS, fs is not otherwise reset before do_exit(). do_exit may later (via mm_release in fork.c) do a put_user to a user-controlled address, potentially allowing a user to leverage an oops into a controlled write into kernel memory. A more logical place to put this might be when we know an oops has occurred, before we call do_exit(), but that would involve changing every architecture, in multiple places. Let's just stick it in do_exit instead. Signed-off-by: Nelson Elhage --- kernel/exit.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 21aa7b3..68899b3 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -914,6 +914,14 @@ NORET_TYPE void do_exit(long code) if (unlikely(!tsk->pid)) panic("Attempted to kill the idle task!"); + /* + * If do_exit is called because this processes oopsed, it's possible + * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before + * continuing. This is relevant at least for clearing clear_child_tid in + * mm_release. + */ + set_fs(USER_DS); + tracehook_report_exit(&code); validate_creds_for_do_exit(tsk); -- 1.7.1.31.g6297e -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/