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From: Kuniyuki Iwashima <kuniyu@amazon.com>
To: <syzbot+42a0dc856239de4de60e@syzkaller.appspotmail.com>
CC: <davem@davemloft.net>, <edumazet@google.com>, <kuba@kernel.org>,
	<linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
	<pabeni@redhat.com>, <syzkaller-bugs@googlegroups.com>, <kuniyu@amazon.com>
Subject: Re: [syzbot] [net?] KMSAN: uninit-value in ipvlan_queue_xmit (2)
Date: Mon, 22 Apr 2024 09:07:28 -0700
Message-ID: <20240422160728.82185-1-kuniyu@amazon.com>
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From: syzbot <syzbot+42a0dc856239de4de60e@syzkaller.appspotmail.com>
Date: Thu, 18 Apr 2024 00:05:21 -0700
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    f2e367d6ad3b Merge tag 'for-6.8/dm-fix-3' of git://git.ker..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=144a8d4a180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1b015d567058472
> dashboard link: https://syzkaller.appspot.com/bug?extid=42a0dc856239de4de60e
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=149caa54180000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10bb8e22180000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/0dabc03369d1/disk-f2e367d6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/240ca250d398/vmlinux-f2e367d6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/cc38bcdb48c9/bzImage-f2e367d6.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+42a0dc856239de4de60e@syzkaller.appspotmail.com
> 
> =====================================================
> BUG: KMSAN: uninit-value in ipvlan_process_outbound drivers/net/ipvlan/ipvlan_core.c:524 [inline]
> BUG: KMSAN: uninit-value in ipvlan_xmit_mode_l3 drivers/net/ipvlan/ipvlan_core.c:602 [inline]
> BUG: KMSAN: uninit-value in ipvlan_queue_xmit+0xf44/0x16b0 drivers/net/ipvlan/ipvlan_core.c:668
>  ipvlan_process_outbound drivers/net/ipvlan/ipvlan_core.c:524 [inline]
>  ipvlan_xmit_mode_l3 drivers/net/ipvlan/ipvlan_core.c:602 [inline]
>  ipvlan_queue_xmit+0xf44/0x16b0 drivers/net/ipvlan/ipvlan_core.c:668
>  ipvlan_start_xmit+0x5c/0x1a0 drivers/net/ipvlan/ipvlan_main.c:222
>  __netdev_start_xmit include/linux/netdevice.h:4989 [inline]
>  netdev_start_xmit include/linux/netdevice.h:5003 [inline]
>  xmit_one net/core/dev.c:3547 [inline]
>  dev_hard_start_xmit+0x244/0xa10 net/core/dev.c:3563
>  __dev_queue_xmit+0x33ed/0x51c0 net/core/dev.c:4351
>  dev_queue_xmit include/linux/netdevice.h:3171 [inline]
>  packet_xmit+0x9c/0x6b0 net/packet/af_packet.c:276
>  packet_snd net/packet/af_packet.c:3081 [inline]
>  packet_sendmsg+0x8aef/0x9f10 net/packet/af_packet.c:3113
>  sock_sendmsg_nosec net/socket.c:730 [inline]
>  __sock_sendmsg net/socket.c:745 [inline]
>  __sys_sendto+0x735/0xa10 net/socket.c:2191
>  __do_sys_sendto net/socket.c:2203 [inline]
>  __se_sys_sendto net/socket.c:2199 [inline]
>  __x64_sys_sendto+0x125/0x1c0 net/socket.c:2199
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x63/0x6b
> 
> Uninit was created at:
>  slab_post_alloc_hook mm/slub.c:3819 [inline]
>  slab_alloc_node mm/slub.c:3860 [inline]
>  __do_kmalloc_node mm/slub.c:3980 [inline]
>  __kmalloc_node_track_caller+0x705/0x1000 mm/slub.c:4001
>  kmalloc_reserve+0x249/0x4a0 net/core/skbuff.c:582
>  __alloc_skb+0x352/0x790 net/core/skbuff.c:651
>  skb_segment+0x20aa/0x7080 net/core/skbuff.c:4647
>  udp6_ufo_fragment+0xcab/0x1150 net/ipv6/udp_offload.c:109
>  ipv6_gso_segment+0x14be/0x2ca0 net/ipv6/ip6_offload.c:152
>  skb_mac_gso_segment+0x3e8/0x760 net/core/gso.c:53
>  nsh_gso_segment+0x6f4/0xf70 net/nsh/nsh.c:108
>  skb_mac_gso_segment+0x3e8/0x760 net/core/gso.c:53
>  __skb_gso_segment+0x4b0/0x730 net/core/gso.c:124
>  skb_gso_segment include/net/gso.h:83 [inline]
>  validate_xmit_skb+0x107f/0x1930 net/core/dev.c:3628
>  __dev_queue_xmit+0x1f28/0x51c0 net/core/dev.c:4343
>  dev_queue_xmit include/linux/netdevice.h:3171 [inline]
>  packet_xmit+0x9c/0x6b0 net/packet/af_packet.c:276
>  packet_snd net/packet/af_packet.c:3081 [inline]
>  packet_sendmsg+0x8aef/0x9f10 net/packet/af_packet.c:3113
>  sock_sendmsg_nosec net/socket.c:730 [inline]
>  __sock_sendmsg net/socket.c:745 [inline]
>  __sys_sendto+0x735/0xa10 net/socket.c:2191
>  __do_sys_sendto net/socket.c:2203 [inline]
>  __se_sys_sendto net/socket.c:2199 [inline]
>  __x64_sys_sendto+0x125/0x1c0 net/socket.c:2199
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x63/0x6b
> 
> CPU: 1 PID: 5101 Comm: syz-executor421 Not tainted 6.8.0-rc5-syzkaller-00297-gf2e367d6ad3b #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
> =====================================================
[...]
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git f2e367d6ad3bdc527c2b14e759c2f010d6b2b7a1

diff --git a/net/nsh/nsh.c b/net/nsh/nsh.c
index f4a38bd6a7e0..1344653916c4 100644
--- a/net/nsh/nsh.c
+++ b/net/nsh/nsh.c
@@ -77,13 +77,15 @@ EXPORT_SYMBOL_GPL(nsh_pop);
 static struct sk_buff *nsh_gso_segment(struct sk_buff *skb,
 				       netdev_features_t features)
 {
+	unsigned int tnl_hlen, mac_len, nsh_len;
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	u16 mac_offset = skb->mac_header;
-	unsigned int nsh_len, mac_len;
-	__be16 proto;
+	__be16 tnl_proto, proto;
 
 	skb_reset_network_header(skb);
 
+	tnl_proto = skb->protocol;
+	tnl_hlen = skb->network_header - skb->mac_header;
 	mac_len = skb->mac_len;
 
 	if (unlikely(!pskb_may_pull(skb, NSH_BASE_HDR_LEN)))
@@ -113,11 +115,11 @@ static struct sk_buff *nsh_gso_segment(struct sk_buff *skb,
 	}
 
 	for (skb = segs; skb; skb = skb->next) {
-		skb->protocol = htons(ETH_P_NSH);
-		__skb_push(skb, nsh_len);
-		skb->mac_header = mac_offset;
-		skb->network_header = skb->mac_header + mac_len;
+		__skb_push(skb, nsh_len + tnl_hlen);
+		skb_reset_mac_header(skb);
+		skb->network_header = skb->mac_header + tnl_hlen;
 		skb->mac_len = mac_len;
+		skb->protocol = tnl_proto;
 	}
 
 out: