linux-kernel - [PATCH 3.18 18/39] md/raid5: fix another livelock caused by non-aligned writes.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon,  9 Feb 2015 16:34:01 +0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Mikulas Patocka <mpatocka@...hat.com>,
	Heinz Mauelshagen <heinzm@...hat.com>,
	NeilBrown <neilb@...e.de>
Subject: [PATCH 3.18 18/39] md/raid5: fix another livelock caused by non-aligned writes.

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@...e.de>

commit b1b02fe97f75b12ab34b2303bfd4e3526d903a58 upstream.

If a non-page-aligned write is destined for a device which
is missing/faulty, we can deadlock.

As the target device is missing, a read-modify-write cycle
is not possible.
As the write is not for a full-page, a recontruct-write cycle
is not possible.

This should be handled by logic in fetch_block() which notices
there is a non-R5_OVERWRITE write to a missing device, and so
loads all blocks.

However since commit 67f455486d2ea2, that code requires
STRIPE_PREREAD_ACTIVE before it will active, and those circumstances
never set STRIPE_PREREAD_ACTIVE.

So: in handle_stripe_dirtying, if neither rmw or rcw was possible,
set STRIPE_DELAYED, which will cause STRIPE_PREREAD_ACTIVE be set
after a suitable delay.

Fixes: 67f455486d2ea20b2d94d6adf5b9b783d079e321
Reported-by: Mikulas Patocka <mpatocka@...hat.com>
Tested-by: Heinz Mauelshagen <heinzm@...hat.com>
Signed-off-by: NeilBrown <neilb@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/raid5.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3195,6 +3195,11 @@ static void handle_stripe_dirtying(struc
 					  (unsigned long long)sh->sector,
 					  rcw, qread, test_bit(STRIPE_DELAYED, &sh->state));
 	}
+
+	if (rcw > disks && rmw > disks &&
+	    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+		set_bit(STRIPE_DELAYED, &sh->state);
+
 	/* now if nothing is locked, and if we have enough data,
 	 * we can start a write request
 	 */

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/