linux-kernel - Re: mainline boot is broken: KASAN: use-after-free in blk_flush_complete

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Date:   Sat, 9 Jun 2018 06:33:06 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Dmitry Vyukov <dvyukov@...gle.com>, linux-block@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: mainline boot is broken: KASAN: use-after-free in
 blk_flush_complete_seq

On 6/9/18 3:34 AM, Dmitry Vyukov wrote:
> Hi,
> 
> Boot of mainline kernel is currently broken.
> On commit 7d3bf613e99abbd96ac7b90ee3694a246c975021.
> Config:
> https://gist.githubusercontent.com/dvyukov/9f7f1fd9e477efd85b221b3a21036c20/raw/7c56ede0840494b26045976960866f2b265c6f64/gistfile1.txt
> Should have been introduced very recently.

Can you try the below?

> You may need to also patch "umh: fix race condition", because that's
> another boot crasher currently present in tree.

Not sure that that refers to.


diff --git a/block/blk-flush.c b/block/blk-flush.c
index 058abdb50f31..ce41f666de3e 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -169,9 +169,11 @@ static bool blk_flush_complete_seq(struct request *rq,
 	struct request_queue *q = rq->q;
 	struct list_head *pending = &fq->flush_queue[fq->flush_pending_idx];
 	bool queued = false, kicked;
+	unsigned int cmd_flags;
 
 	BUG_ON(rq->flush.seq & seq);
 	rq->flush.seq |= seq;
+	cmd_flags = rq->cmd_flags;
 
 	if (likely(!error))
 		seq = blk_flush_cur_seq(rq);
@@ -212,7 +214,7 @@ static bool blk_flush_complete_seq(struct request *rq,
 		BUG();
 	}
 
-	kicked = blk_kick_flush(q, fq, rq->cmd_flags);
+	kicked = blk_kick_flush(q, fq, cmd_flags);
 	return kicked | queued;
 }
 

-- 
Jens Axboe