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

From: syzbot
Date: Thu Jan 11 2024 - 15:35:10 EST

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***

Subject: Re: [syzbot] [net?] KMSAN: uninit-value in validate_xmit_skb
Author: edumazet@xxxxxxxxxx

On Thu, Jan 11, 2024 at 9:32 PM syzbot
<syzbot+7f4d0ea3df4d4fa9a65f@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> > On Thu, Jan 11, 2024 at 9:27 PM syzbot
> > <syzbot+7f4d0ea3df4d4fa9a65f@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >>
> >> Hello,
> >>
> >> syzbot found the following issue on:
> >>
> >> HEAD commit: fbafc3e621c3 Merge tag 'for_linus' of git://git.kernelorg..
> >> 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+7f4d0ea3df4d4fa9a65f@xxxxxxxxxxxxxxxxxxxxxxxxx
> >>
> >> =====================================================
> >> 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.
> >> See https://goo.gl/tpsmEJ for more information about syzbot.
> >> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
> >>
> >> syzbot will keep track of this issue. See:
> >> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> >>
> >> If the report is already addressed, let syzbot know by replying with:
> >> #syz fix: exact-commit-title
> >>
> >> 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.
> >>
> >> If you want to overwrite report's subsystems, reply with:
> >> #syz set subsystems: new-subsystem
> >> (See the list of subsystem names on the web dashboard)
> >>
> >> If the report is a duplicate of another one, reply with:
> >> #syz dup: exact-subject-of-another-report
> >>
> >> If you want to undo deduplication, reply with:
> >> #syz undup
> >
> > #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

```
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;
}
```