[syzbot] [net?] KMSAN: uninit-value in validate_xmit_skb

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fbafc3e621c3 Merge tag 'for_linus' of git://git.kernel.org..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1135ab95e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=e0c7078a6b901aa3
dashboard link: https://syzkaller.appspot.com/bug?extid=7f4d0ea3df4d4fa9a65f
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=15e15379e80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=170f6981e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1520f7b6daa4/disk-fbafc3e6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8b490af009d5/vmlinux-fbafc3e6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/202ca200f4a4/bzImage-fbafc3e6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7f4d0e...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in skb_gso_segment include/net/gso.h:83 [inline]
BUG: KMSAN: uninit-value in validate_xmit_skb+0x10f2/0x1930 net/core/dev.c:3629
skb_gso_segment include/net/gso.h:83 [inline]
validate_xmit_skb+0x10f2/0x1930 net/core/dev.c:3629
__dev_queue_xmit+0x1eac/0x5130 net/core/dev.c:4341
dev_queue_xmit include/linux/netdevice.h:3134 [inline]
packet_xmit+0x9c/0x6b0 net/packet/af_packet.c:276
packet_snd net/packet/af_packet.c:3087 [inline]
packet_sendmsg+0x8b1d/0x9f30 net/packet/af_packet.c:3119
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
__sys_sendmsg net/socket.c:2667 [inline]
__do_sys_sendmsg net/socket.c:2676 [inline]
__se_sys_sendmsg net/socket.c:2674 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:
slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
slab_alloc_node mm/slub.c:3478 [inline]
kmem_cache_alloc_node+0x5e9/0xb10 mm/slub.c:3523
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:560
__alloc_skb+0x318/0x740 net/core/skbuff.c:651
alloc_skb include/linux/skbuff.h:1286 [inline]
alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6334
sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2780
packet_alloc_skb net/packet/af_packet.c:2936 [inline]
packet_snd net/packet/af_packet.c:3030 [inline]
packet_sendmsg+0x70e8/0x9f30 net/packet/af_packet.c:3119
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
__sys_sendmsg net/socket.c:2667 [inline]
__do_sys_sendmsg net/socket.c:2676 [inline]
__se_sys_sendmsg net/socket.c:2674 [inline]
__x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

CPU: 0 PID: 5025 Comm: syz-executor279 Not tainted 6.7.0-rc7-syzkaller-00003-gfbafc3e621c3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
=====================================================


---
This report is generated by a bot. It may contain errors.
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[Eric Dumazet]

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

```
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 27cc1d4643219a44c01a2404124cd45ef46f7f3d..4dfa9b69ca8d95d43e44831bc166eadbe5715d3c
100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -3,6 +3,8 @@
#define _LINUX_VIRTIO_NET_H

#include <linux/if_vlan.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
#include <linux/udp.h>
#include <uapi/linux/tcp.h>
#include <uapi/linux/virtio_net.h>
@@ -49,6 +51,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
const struct virtio_net_hdr *hdr,
bool little_endian)
{
+ unsigned int nh_min_len = sizeof(struct iphdr);
unsigned int gso_type = 0;
unsigned int thlen = 0;
unsigned int p_off = 0;
@@ -65,6 +68,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
gso_type = SKB_GSO_TCPV6;
ip_proto = IPPROTO_TCP;
thlen = sizeof(struct tcphdr);
+ nh_min_len = sizeof(struct ipv6hdr);
break;
case VIRTIO_NET_HDR_GSO_UDP:
gso_type = SKB_GSO_UDP;
@@ -100,7 +104,8 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
if (!skb_partial_csum_set(skb, start, off))
return -EINVAL;

- p_off = skb_transport_offset(skb) + thlen;
+ nh_min_len = max_t(u32, nh_min_len, skb_transport_offset(skb));
+ p_off = nh_min_len + thlen;
if (!pskb_may_pull(skb, p_off))
return -EINVAL;
} else {
@@ -140,7 +145,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,

skb_set_transport_header(skb, keys.control.thoff);
} else if (gso_type) {
- p_off = thlen;
+ p_off = nh_min_len + thlen;
if (!pskb_may_pull(skb, p_off))
return -EINVAL;
}
```

[syzbot]

want either no args or 2 args (repo, branch), got 1

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: Re: [syzbot] [net?] KMSAN: uninit-value in validate_xmit_skb
Author: edum...@google.com

On Thu, Jan 11, 2024 at 9:32 PM syzbot
<syzbot+7f4d0e...@syzkaller.appspotmail.com> wrote:
>
> > On Thu, Jan 11, 2024 at 9:27 PM syzbot
> > <syzbot+7f4d0e...@syzkaller.appspotmail.com> wrote:
> >>

> > #syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>
> want either no args or 2 args (repo, branch), got 1

#syz test

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to apply patch:
checking file include/linux/virtio_net.h
patch: **** unexpected end of file in patch



Tested on:

commit: 70d201a4 Merge tag 'f2fs-for-6.8-rc1' of git://git.ker..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=e0c7078a6b901aa3
dashboard link: https://syzkaller.appspot.com/bug?extid=7f4d0ea3df4d4fa9a65f
compiler:

patch: https://syzkaller.appspot.com/x/patch.diff?x=11c430a5e80000