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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, "Blank-Burian, Markus,
	Dr." <blankburian@uni-muenster.de>,
	Ming Lei <ming.lei@redhat.com>, Christoph Hellwig <hch@lst.de>,
	John Garry <john.garry@huawei.com>, Jens Axboe <axboe@kernel.dk>,
	Yi Zhang <yi.zhang@redhat.com>
Subject: [PATCH 5.13 05/22] blk-mq: fix kernel panic during iterating over flush request
Date: Fri, 10 Sep 2021 14:30:04 +0200	[thread overview]
Message-ID: <20210910122916.112316793@linuxfoundation.org> (raw)
In-Reply-To: <20210910122915.942645251@linuxfoundation.org>

From: Ming Lei <ming.lei@redhat.com>

commit c2da19ed50554ce52ecbad3655c98371fe58599f upstream.

For fixing use-after-free during iterating over requests, we grabbed
request's refcount before calling ->fn in commit 2e315dc07df0 ("blk-mq:
grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter").
Turns out this way may cause kernel panic when iterating over one flush
request:

1) old flush request's tag is just released, and this tag is reused by
one new request, but ->rqs[] isn't updated yet

2) the flush request can be re-used for submitting one new flush command,
so blk_rq_init() is called at the same time

3) meantime blk_mq_queue_tag_busy_iter() is called, and old flush request
is retrieved from ->rqs[tag]; when blk_mq_put_rq_ref() is called,
flush_rq->end_io may not be updated yet, so NULL pointer dereference
is triggered in blk_mq_put_rq_ref().

Fix the issue by calling refcount_set(&flush_rq->ref, 1) after
flush_rq->end_io is set. So far the only other caller of blk_rq_init() is
scsi_ioctl_reset() in which the request doesn't enter block IO stack and
the request reference count isn't used, so the change is safe.

Fixes: 2e315dc07df0 ("blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter")
Reported-by: "Blank-Burian, Markus, Dr." <blankburian@uni-muenster.de>
Tested-by: "Blank-Burian, Markus, Dr." <blankburian@uni-muenster.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20210811142624.618598-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Cc: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 block/blk-core.c  |    1 -
 block/blk-flush.c |    8 ++++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -122,7 +122,6 @@ void blk_rq_init(struct request_queue *q
 	rq->internal_tag = BLK_MQ_NO_TAG;
 	rq->start_time_ns = ktime_get_ns();
 	rq->part = NULL;
-	refcount_set(&rq->ref, 1);
 	blk_crypto_rq_set_defaults(rq);
 }
 EXPORT_SYMBOL(blk_rq_init);
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -329,6 +329,14 @@ static void blk_kick_flush(struct reques
 	flush_rq->rq_flags |= RQF_FLUSH_SEQ;
 	flush_rq->rq_disk = first_rq->rq_disk;
 	flush_rq->end_io = flush_end_io;
+	/*
+	 * Order WRITE ->end_io and WRITE rq->ref, and its pair is the one
+	 * implied in refcount_inc_not_zero() called from
+	 * blk_mq_find_and_get_req(), which orders WRITE/READ flush_rq->ref
+	 * and READ flush_rq->end_io
+	 */
+	smp_wmb();
+	refcount_set(&flush_rq->ref, 1);
 
 	blk_flush_queue_rq(flush_rq, false);
 }



  parent reply	other threads:[~2021-09-10 12:33 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-10 12:29 [PATCH 5.13 00/22] 5.13.16-rc1 review Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 01/22] firmware: dmi: Move product_sku info to the end of the modalias Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 02/22] igmp: Add ip_mc_list lock in ip_check_mc_rcu Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 03/22] net: ll_temac: Remove left-over debug message Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 04/22] Revert "r8169: avoid link-up interrupt issue on RTL8106e if user enables ASPM" Greg Kroah-Hartman
2021-09-10 12:30 ` Greg Kroah-Hartman [this message]
2021-09-10 12:30 ` [PATCH 5.13 06/22] blk-mq: fix is_flush_rq Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 07/22] blk-mq: clearing flush request reference in tags->rqs[] Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 08/22] ALSA: usb-audio: Add registration quirk for JBL Quantum 800 Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 09/22] Bluetooth: Add additional Bluetooth part for Realtek 8852AE Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 10/22] Bluetooth: btusb: Make the CSR clone chip force-suspend workaround more generic Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 11/22] usb: host: xhci-rcar: Dont reload firmware after the completion Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 12/22] usb: xhci-mtk: fix issue of out-of-bounds array access Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 13/22] usb: cdnsp: fix the wrong mult value for HS isoc or intr Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 14/22] usb: gadget: tegra-xudc: " Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 15/22] usb: mtu3: restore HS function when set SS/SSP Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 16/22] usb: mtu3: use @mult for HS isoc or intr Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 17/22] usb: mtu3: fix the wrong HS mult value Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 18/22] xhci: fix even more unsafe memory usage in xhci tracing Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 19/22] xhci: fix " Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 20/22] xhci: Fix failure to give back some cached cancelled URBs Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 21/22] x86/reboot: Limit Dell Optiplex 990 quirk to early BIOS versions Greg Kroah-Hartman
2021-09-10 12:30 ` [PATCH 5.13 22/22] PCI: Call Max Payload Size-related fixup quirks early Greg Kroah-Hartman
2021-09-10 18:38 ` [PATCH 5.13 00/22] 5.13.16-rc1 review Fox Chen
2021-09-10 19:43 ` Florian Fainelli
2021-09-10 23:17 ` Shuah Khan
2021-09-11 16:20 ` Justin Forbes
2021-09-11 19:36 ` Guenter Roeck
2021-09-12  0:48 ` Daniel Díaz

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