Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756549AbaAMRGw (ORCPT ); Mon, 13 Jan 2014 12:06:52 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:52923 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753327AbaAMQBe (ORCPT ); Mon, 13 Jan 2014 11:01:34 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Junho Ryu , "Theodore Ts'o" , Luis Henriques Subject: [PATCH 3.11 028/208] ext4: fix use-after-free in ext4_mb_new_blocks Date: Mon, 13 Jan 2014 15:57:49 +0000 Message-Id: <1389628849-1614-29-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1389628849-1614-1-git-send-email-luis.henriques@canonical.com> References: <1389628849-1614-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.11.10.3 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Junho Ryu commit 4e8d2139802ce4f41936a687f06c560b12115247 upstream. ext4_mb_put_pa should hold pa->pa_lock before accessing pa->pa_count. While ext4_mb_use_preallocated checks pa->pa_deleted first and then increments pa->count later, ext4_mb_put_pa decrements pa->pa_count before holding pa->pa_lock and then sets pa->pa_deleted. * Free sequence ext4_mb_put_pa (1): atomic_dec_and_test pa->pa_count ext4_mb_put_pa (2): lock pa->pa_lock ext4_mb_put_pa (3): check pa->pa_deleted ext4_mb_put_pa (4): set pa->pa_deleted=1 ext4_mb_put_pa (5): unlock pa->pa_lock ext4_mb_put_pa (6): remove pa from a list ext4_mb_pa_callback: free pa * Use sequence ext4_mb_use_preallocated (1): iterate over preallocation ext4_mb_use_preallocated (2): lock pa->pa_lock ext4_mb_use_preallocated (3): check pa->pa_deleted ext4_mb_use_preallocated (4): increase pa->pa_count ext4_mb_use_preallocated (5): unlock pa->pa_lock ext4_mb_release_context: access pa * Use-after-free sequence [initial status] pa_deleted = 0, pa_count = 1> ext4_mb_use_preallocated (1): iterate over preallocation ext4_mb_use_preallocated (2): lock pa->pa_lock ext4_mb_use_preallocated (3): check pa->pa_deleted ext4_mb_put_pa (1): atomic_dec_and_test pa->pa_count [pa_count decremented] pa_deleted = 0, pa_count = 0> ext4_mb_use_preallocated (4): increase pa->pa_count [pa_count incremented] pa_deleted = 0, pa_count = 1> ext4_mb_use_preallocated (5): unlock pa->pa_lock ext4_mb_put_pa (2): lock pa->pa_lock ext4_mb_put_pa (3): check pa->pa_deleted ext4_mb_put_pa (4): set pa->pa_deleted=1 [race condition!] pa_deleted = 1, pa_count = 1> ext4_mb_put_pa (5): unlock pa->pa_lock ext4_mb_put_pa (6): remove pa from a list ext4_mb_pa_callback: free pa ext4_mb_release_context: access pa AddressSanitizer has detected use-after-free in ext4_mb_new_blocks Bug report: http://goo.gl/rG1On3 Signed-off-by: Junho Ryu Signed-off-by: "Theodore Ts'o" Signed-off-by: Luis Henriques --- fs/ext4/mballoc.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 4bbbf13b..f243825 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -3424,6 +3424,9 @@ static void ext4_mb_pa_callback(struct rcu_head *head) { struct ext4_prealloc_space *pa; pa = container_of(head, struct ext4_prealloc_space, u.pa_rcu); + + BUG_ON(atomic_read(&pa->pa_count)); + BUG_ON(pa->pa_deleted == 0); kmem_cache_free(ext4_pspace_cachep, pa); } @@ -3437,11 +3440,13 @@ static void ext4_mb_put_pa(struct ext4_allocation_context *ac, ext4_group_t grp; ext4_fsblk_t grp_blk; - if (!atomic_dec_and_test(&pa->pa_count) || pa->pa_free != 0) - return; - /* in this short window concurrent discard can set pa_deleted */ spin_lock(&pa->pa_lock); + if (!atomic_dec_and_test(&pa->pa_count) || pa->pa_free != 0) { + spin_unlock(&pa->pa_lock); + return; + } + if (pa->pa_deleted == 1) { spin_unlock(&pa->pa_lock); return; -- 1.8.3.2 -- 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/