linux-kernel - Re: general protection fault in xfrm_user_rcv_msg

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Date:   Tue, 23 Feb 2021 14:44:50 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     syzbot <syzbot+5078fc2d7cf37d71de1c@...kaller.appspotmail.com>
Cc:     David Miller <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Jakub Kicinski <kuba@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: general protection fault in xfrm_user_rcv_msg_compat

On Tue, Feb 23, 2021 at 6:55 AM syzbot
<syzbot+5078fc2d7cf37d71de1c@...kaller.appspotmail.com> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    a99163e9 Merge tag 'devicetree-for-5.12' of git://git.kern..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11a6fccad00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7a875029a795d230
> dashboard link: https://syzkaller.appspot.com/bug?extid=5078fc2d7cf37d71de1c
> userspace arch: i386
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=167c1832d00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10214f12d00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+5078fc2d7cf37d71de1c@...kaller.appspotmail.com
>
> general protection fault, probably for non-canonical address 0xe51af2c1f2c7bd20: 0000 [#1] PREEMPT SMP KASAN
> KASAN: maybe wild-memory-access in range [0x28d7b60f963de900-0x28d7b60f963de907]
> CPU: 1 PID: 8357 Comm: syz-executor113 Not tainted 5.11.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:nla_type include/net/netlink.h:1130 [inline]
> RIP: 0010:xfrm_xlate32_attr net/xfrm/xfrm_compat.c:404 [inline]
> RIP: 0010:xfrm_xlate32 net/xfrm/xfrm_compat.c:526 [inline]
> RIP: 0010:xfrm_user_rcv_msg_compat+0x5e5/0x1070 net/xfrm/xfrm_compat.c:571

Looks like we have to initialize the pointer array to NULL's.

diff --git a/net/xfrm/xfrm_compat.c b/net/xfrm/xfrm_compat.c
index d8e8a11ca845..56fb32f90799 100644
--- a/net/xfrm/xfrm_compat.c
+++ b/net/xfrm/xfrm_compat.c
@@ -537,7 +537,7 @@ static struct nlmsghdr
*xfrm_user_rcv_msg_compat(const struct nlmsghdr *h32,
 {
        /* netlink_rcv_skb() checks if a message has full (struct nlmsghdr) */
        u16 type = h32->nlmsg_type - XFRM_MSG_BASE;
-       struct nlattr *attrs[XFRMA_MAX+1];
+       struct nlattr *attrs[XFRMA_MAX+1] = {0};
        struct nlmsghdr *h64;
        size_t len;
        int err;