From: Pavel Skripkin <paskripkin@gmail•com>
To: syzbot <syzbot+e6741b97d5552f97c24d@syzkaller•appspotmail.com>
Cc: davem@davemloft•net, devicetree@vger•kernel.org,
frowand.list@gmail•com, gregkh@linuxfoundation•org,
jmaloy@redhat•com, kuba@kernel•org, linux-kernel@vger•kernel.org,
netdev@vger•kernel.org, rafael@kernel•org, robh+dt@kernel•org,
robh@kernel•org, syzkaller-bugs@googlegroups•com,
tipc-discussion@lists•sourceforge.net, ying.xue@windriver•com
Subject: Re: [syzbot] KASAN: use-after-free Read in tipc_recvmsg
Date: Fri, 23 Jul 2021 19:49:32 +0300 [thread overview]
Message-ID: <20210723194932.6c3b77a8@gmail.com> (raw)
In-Reply-To: <20210723193611.746e7071@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 2201 bytes --]
On Fri, 23 Jul 2021 19:36:11 +0300
Pavel Skripkin <paskripkin@gmail•com> wrote:
> On Sun, 18 Jul 2021 10:15:19 -0700
> syzbot <syzbot+e6741b97d5552f97c24d@syzkaller•appspotmail.com> wrote:
>
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: ab0441b4a920 Merge branch 'vmxnet3-version-6'
> > git tree: net-next
> > console output:
> > https://syzkaller.appspot.com/x/log.txt?x=1744ac6a300000 kernel
> > config: https://syzkaller.appspot.com/x/.config?x=da140227e4f25b17
> > dashboard link:
> > https://syzkaller.appspot.com/bug?extid=e6741b97d5552f97c24d syz
> > repro:
> > https://syzkaller.appspot.com/x/repro.syz?x=13973a74300000 C
> > reproducer:
> > https://syzkaller.appspot.com/x/repro.c?x=17ffc902300000
> >
> > The issue was bisected to:
> >
> > commit 67a3156453859ceb40dc4448b7a6a99ea0ad27c7
> > Author: Rob Herring <robh@kernel•org>
> > Date: Thu May 27 19:45:47 2021 +0000
> >
> > of: Merge of_address_to_resource() and
> > of_pci_address_to_resource() implementations
> >
> > bisection log:
> > https://syzkaller.appspot.com/x/bisect.txt?x=129b0438300000 final
> > oops:
> > https://syzkaller.appspot.com/x/report.txt?x=119b0438300000 console
> > output: https://syzkaller.appspot.com/x/log.txt?x=169b0438300000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the
> > commit: Reported-by:
> > syzbot+e6741b97d5552f97c24d@syzkaller•appspotmail.com Fixes:
> > 67a315645385 ("of: Merge of_address_to_resource() and
> > of_pci_address_to_resource() implementations")
> >
> > ==================================================================
> > BUG: KASAN: use-after-free in tipc_recvmsg+0xf77/0xf90
> > net/tipc/socket.c:1979 Read of size 4 at addr ffff8880328cf1c0 by
> > task kworker/u4:0/8
> >
>
> Since code accesing skb_cb after possible kfree_skb() call let's just
> store bytes_read to variable and use it instead of acessing
> skb_cb->bytes_read
>
> #syz test
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> master
>
>
Oops... The buggy code is in -next tree.
#syz test
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
With regards,
Pavel Skripkin
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From 9f81f8574bfc1183209022b405848e01c35b86e6 Mon Sep 17 00:00:00 2001
From: Pavel Skripkin <paskripkin@gmail•com>
Date: Fri, 23 Jul 2021 19:34:06 +0300
Subject: [PATCH] tipc: fix use-after-free in tipc_recvmsg
/* .. */
Signed-off-by: Pavel Skripkin <paskripkin@gmail•com>
---
net/tipc/socket.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 9b0b311c7ec1..0cf2468d209d 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1886,6 +1886,7 @@ static int tipc_recvmsg(struct socket *sock, struct msghdr *m,
struct sk_buff *skb;
bool grp_evt;
long timeout;
+ unsigned int bytes_read;
/* Catch invalid receive requests */
if (unlikely(!buflen))
@@ -1973,10 +1974,13 @@ static int tipc_recvmsg(struct socket *sock, struct msghdr *m,
tipc_node_distr_xmit(sock_net(sk), &xmitq);
}
- if (!skb_cb->bytes_read)
+ /* To avoid accesing skb_cb after tsk_advance_rx_queue */
+ bytes_read = skb_cb->bytes_read;
+
+ if (!bytes_read)
tsk_advance_rx_queue(sk);
- if (likely(!connected) || skb_cb->bytes_read)
+ if (likely(!connected) || bytes_read)
goto exit;
/* Send connection flow control advertisement when applicable */
--
2.32.0
next prev parent reply other threads:[~2021-07-23 16:49 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-18 17:15 [syzbot] KASAN: use-after-free Read in tipc_recvmsg syzbot
2021-07-23 16:36 ` Pavel Skripkin
2021-07-23 16:41 ` Xin Long
2021-07-23 16:52 ` Pavel Skripkin
2021-07-23 16:49 ` Pavel Skripkin [this message]
2021-07-23 23:10 ` syzbot
2021-07-23 22:51 ` syzbot
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