[syzbot] [net?] KMSAN: uninit-value in ipvlan_queue_xmit (2)

[syzbot]

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+42a0dc...@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
=====================================================


---
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[Eric Dumazet]

Cc Kuniyuki Iwashima

This is the syzbot bug I mentioned earlier to you.

Thanks !

[Kuniyuki Iwashima]

From: Eric Dumazet <edum...@google.com>
Date: Thu, 18 Apr 2024 09:19:20 +0200

Will look into it.

Thanks!

[Kuniyuki Iwashima]

From: syzbot <syzbot+42a0dc...@syzkaller.appspotmail.com>
Date: Thu, 18 Apr 2024 00:05:21 -0700

[...]

> 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:

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+42a0dc...@syzkaller.appspotmail.com

Tested on:

commit: f2e367d6 Merge tag 'for-6.8/dm-fix-3' of git://git.ker..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1286b06b180000

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

patch: https://syzkaller.appspot.com/x/patch.diff?x=117ae96f180000

Note: testing is done by a robot and is best-effort only.