Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934442AbaGOXjL (ORCPT ); Tue, 15 Jul 2014 19:39:11 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:45407 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933941AbaGOXOK (ORCPT ); Tue, 15 Jul 2014 19:14:10 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Minfei Huang , Joe Thornber , Mike Snitzer , Mikulas Patocka Subject: [PATCH 3.15 42/84] dm io: fix a race condition in the wake up code for sync_io Date: Tue, 15 Jul 2014 16:17:39 -0700 Message-Id: <20140715231714.461216059@linuxfoundation.org> X-Mailer: git-send-email 2.0.0.254.g50f84e3 In-Reply-To: <20140715231713.193785557@linuxfoundation.org> References: <20140715231713.193785557@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Joe Thornber commit 10f1d5d111e8aed46a0f1179faf9a3cf422f689e upstream. There's a race condition between the atomic_dec_and_test(&io->count) in dec_count() and the waking of the sync_io() thread. If the thread is spuriously woken immediately after the decrement it may exit, making the on stack io struct invalid, yet the dec_count could still be using it. Fix this race by using a completion in sync_io() and dec_count(). Reported-by: Minfei Huang Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Acked-by: Mikulas Patocka Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-io.c | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-) --- a/drivers/md/dm-io.c +++ b/drivers/md/dm-io.c @@ -10,6 +10,7 @@ #include #include +#include #include #include #include @@ -32,7 +33,7 @@ struct dm_io_client { struct io { unsigned long error_bits; atomic_t count; - struct task_struct *sleeper; + struct completion *wait; struct dm_io_client *client; io_notify_fn callback; void *context; @@ -121,8 +122,8 @@ static void dec_count(struct io *io, uns invalidate_kernel_vmap_range(io->vma_invalidate_address, io->vma_invalidate_size); - if (io->sleeper) - wake_up_process(io->sleeper); + if (io->wait) + complete(io->wait); else { unsigned long r = io->error_bits; @@ -387,6 +388,7 @@ static int sync_io(struct dm_io_client * */ volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1]; struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io)); + DECLARE_COMPLETION_ONSTACK(wait); if (num_regions > 1 && (rw & RW_MASK) != WRITE) { WARN_ON(1); @@ -395,7 +397,7 @@ static int sync_io(struct dm_io_client * io->error_bits = 0; atomic_set(&io->count, 1); /* see dispatch_io() */ - io->sleeper = current; + io->wait = &wait; io->client = client; io->vma_invalidate_address = dp->vma_invalidate_address; @@ -403,15 +405,7 @@ static int sync_io(struct dm_io_client * dispatch_io(rw, num_regions, where, dp, io, 1); - while (1) { - set_current_state(TASK_UNINTERRUPTIBLE); - - if (!atomic_read(&io->count)) - break; - - io_schedule(); - } - set_current_state(TASK_RUNNING); + wait_for_completion_io(&wait); if (error_bits) *error_bits = io->error_bits; @@ -434,7 +428,7 @@ static int async_io(struct dm_io_client io = mempool_alloc(client->pool, GFP_NOIO); io->error_bits = 0; atomic_set(&io->count, 1); /* see dispatch_io() */ - io->sleeper = NULL; + io->wait = NULL; io->client = client; io->callback = fn; io->context = context; -- 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/