Stable Archive on lore.kernel.org
 help / color / Atom feed
From: Sasha Levin <sashal@kernel.org>
To: gregkh@linuxfoundation.org
Cc: tj@kernel.org, akpm@linux-foundation.org, axboe@kernel.dk,
	clm@fb.com, jack@suse.cz, stable@vger.kernel.org,
	torvalds@linux-foundation.org
Subject: Re: FAILED: patch "[PATCH] writeback: fix use-after-free in finish_writeback_work()" failed to apply to 5.3-stable tree
Date: Sat, 12 Oct 2019 10:34:02 -0400
Message-ID: <20191012143402.GA15167@sasha-vm> (raw)
In-Reply-To: <157086827811218@kroah.com>

On Sat, Oct 12, 2019 at 10:17:58AM +0200, gregkh@linuxfoundation.org wrote:
>
>The patch below does not apply to the 5.3-stable tree.
>If someone wants it applied there, or to any other stable or longterm
>tree, then please email the backport, including the original git commit
>id to <stable@vger.kernel.org>.
>
>thanks,
>
>greg k-h
>
>------------------ original commit in Linus's tree ------------------
>
>From 8e00c4e9dd852f7a9bf12234fad65a2f2f93788f Mon Sep 17 00:00:00 2001
>From: Tejun Heo <tj@kernel.org>
>Date: Sun, 6 Oct 2019 17:58:09 -0700
>Subject: [PATCH] writeback: fix use-after-free in finish_writeback_work()
>
>finish_writeback_work() reads @done->waitq after decrementing
>@done->cnt.  However, once @done->cnt reaches zero, @done may be freed
>(from stack) at any moment and @done->waitq can contain something
>unrelated by the time finish_writeback_work() tries to read it.  This
>led to the following crash.
>
>  "BUG: kernel NULL pointer dereference, address: 0000000000000002"
>  #PF: supervisor write access in kernel mode
>  #PF: error_code(0x0002) - not-present page
>  PGD 0 P4D 0
>  Oops: 0002 [#1] SMP DEBUG_PAGEALLOC
>  CPU: 40 PID: 555153 Comm: kworker/u98:50 Kdump: loaded Not tainted
>  ...
>  Workqueue: writeback wb_workfn (flush-btrfs-1)
>  RIP: 0010:_raw_spin_lock_irqsave+0x10/0x30
>  Code: 48 89 d8 5b c3 e8 50 db 6b ff eb f4 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 53 9c 5b fa 31 c0 ba 01 00 00 00 <f0> 0f b1 17 75 05 48 89 d8 5b c3 89 c6 e8 fe ca 6b ff eb f2 66 90
>  RSP: 0018:ffffc90049b27d98 EFLAGS: 00010046
>  RAX: 0000000000000000 RBX: 0000000000000246 RCX: 0000000000000000
>  RDX: 0000000000000001 RSI: 0000000000000003 RDI: 0000000000000002
>  RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
>  R10: ffff889fff407600 R11: ffff88ba9395d740 R12: 000000000000e300
>  R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000000000
>  FS:  0000000000000000(0000) GS:ffff88bfdfa00000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  CR2: 0000000000000002 CR3: 0000000002409005 CR4: 00000000001606e0
>  Call Trace:
>   __wake_up_common_lock+0x63/0xc0
>   wb_workfn+0xd2/0x3e0
>   process_one_work+0x1f5/0x3f0
>   worker_thread+0x2d/0x3d0
>   kthread+0x111/0x130
>   ret_from_fork+0x1f/0x30
>
>Fix it by reading and caching @done->waitq before decrementing
>@done->cnt.
>
>Link: http://lkml.kernel.org/r/20190924010631.GH2233839@devbig004.ftw2.facebook.com
>Fixes: 5b9cce4c7eb069 ("writeback: Generalize and expose wb_completion")

Hm... 5b9cce4c7eb069 went upstream during the 5.4 merge window, but:

>Signed-off-by: Tejun Heo <tj@kernel.org>
>Debugged-by: Chris Mason <clm@fb.com>
>Reviewed-by: Jens Axboe <axboe@kernel.dk>
>Cc: Jan Kara <jack@suse.cz>
>Cc: <stable@vger.kernel.org>	[5.2+]

This tag says that 8e00c4e9dd85 should be backported to 5.3.

-- 
Thanks,
Sasha

  reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-12  8:17 gregkh
2019-10-12 14:34 ` Sasha Levin [this message]
2019-10-12 21:54 ` Linus Torvalds
2019-10-14 15:40   ` Tejun Heo

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191012143402.GA15167@sasha-vm \
    --to=sashal@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=axboe@kernel.dk \
    --cc=clm@fb.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=jack@suse.cz \
    --cc=stable@vger.kernel.org \
    --cc=tj@kernel.org \
    --cc=torvalds@linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Stable Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/stable/0 stable/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 stable stable/ https://lore.kernel.org/stable \
		stable@vger.kernel.org
	public-inbox-index stable

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.stable


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git