Message-ID: <91426976-b784-e480-6e3a-52da5d1268cc@gmail.com>
Date:   Sat, 20 Nov 2021 18:02:02 +0300
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Subject: Re: [syzbot] KASAN: use-after-free Read in rxe_queue_cleanup
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To:     syzbot <syzbot+aab53008a5adf26abe91@syzkaller.appspotmail.com>,
        dledford@redhat.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org,
        linux-rdma@vger.kernel.org, netdev@vger.kernel.org,
        syzkaller-bugs@googlegroups.com, zyjzyj2000@gmail.com
References: <000000000000c4e52d05d120e1b0@google.com>
From:   Pavel Skripkin <paskripkin@gmail.com>
In-Reply-To: <000000000000c4e52d05d120e1b0@google.com>
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On 11/19/21 12:27, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    8d0112ac6fd0 Merge tag 'net-5.16-rc2' of git://git.kernel...
> git tree:       net
> console output: https://syzkaller.appspot.com/x/log.txt?x=14e3eeaab00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=6d3b8fd1977c1e73
> dashboard link: https://syzkaller.appspot.com/bug?extid=aab53008a5adf26abe91
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+aab53008a5adf26abe91@syzkaller.appspotmail.com
> 
> Free swap  = 0kB
> Total swap = 0kB
> 2097051 pages RAM
> 0 pages HighMem/MovableOnly
> 384517 pages reserved
> 0 pages cma reserved
> ==================================================================
> BUG: KASAN: use-after-free in rxe_queue_cleanup+0xf4/0x100 drivers/infiniband/sw/rxe/rxe_queue.c:193
> Read of size 8 at addr ffff88814a6b6e90 by task syz-executor.3/9534
> 

On error handling path in rxe_qp_from_init() qp->sq.queue is freed and 
then rxe_create_qp() will drop last reference to this object. qp clean 
up function will try to free this queue one time and it causes UAF bug.

Just for thoughts.


diff --git a/drivers/infiniband/sw/rxe/rxe_qp.c 
b/drivers/infiniband/sw/rxe/rxe_qp.c
index 975321812c87..54b8711321c1 100644
--- a/drivers/infiniband/sw/rxe/rxe_qp.c
+++ b/drivers/infiniband/sw/rxe/rxe_qp.c
@@ -359,6 +359,7 @@ int rxe_qp_from_init(struct rxe_dev *rxe, struct 
rxe_qp *qp, struct rxe_pd *pd,

  err2:
  	rxe_queue_cleanup(qp->sq.queue);
+	qp->sq.queue = NULL;
  err1:
  	qp->pd = NULL;
  	qp->rcq = NULL;


With regards,
Pavel Skripkin