Patch "nsh: Restore skb->{protocol,data,mac_header} for outer header in nsh_gso_segment()." has been added to the 6.6-stable tree

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This is a note to let you know that I've just added the patch titled

    nsh: Restore skb->{protocol,data,mac_header} for outer header in nsh_gso_segment().

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nsh-restore-skb-protocol-data-mac_header-for-outer-h.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3386749c459fc62ef9cb4cf2e839ce751d724182
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date:   Tue Apr 23 19:35:49 2024 -0700

    nsh: Restore skb->{protocol,data,mac_header} for outer header in nsh_gso_segment().
    
    [ Upstream commit 4b911a9690d72641879ea6d13cce1de31d346d79 ]
    
    syzbot triggered various splats (see [0] and links) by a crafted GSO
    packet of VIRTIO_NET_HDR_GSO_UDP layering the following protocols:
    
      ETH_P_8021AD + ETH_P_NSH + ETH_P_IPV6 + IPPROTO_UDP
    
    NSH can encapsulate IPv4, IPv6, Ethernet, NSH, and MPLS.  As the inner
    protocol can be Ethernet, NSH GSO handler, nsh_gso_segment(), calls
    skb_mac_gso_segment() to invoke inner protocol GSO handlers.
    
    nsh_gso_segment() does the following for the original skb before
    calling skb_mac_gso_segment()
    
      1. reset skb->network_header
      2. save the original skb->{mac_heaeder,mac_len} in a local variable
      3. pull the NSH header
      4. resets skb->mac_header
      5. set up skb->mac_len and skb->protocol for the inner protocol.
    
    and does the following for the segmented skb
    
      6. set ntohs(ETH_P_NSH) to skb->protocol
      7. push the NSH header
      8. restore skb->mac_header
      9. set skb->mac_header + mac_len to skb->network_header
     10. restore skb->mac_len
    
    There are two problems in 6-7 and 8-9.
    
      (a)
      After 6 & 7, skb->data points to the NSH header, so the outer header
      (ETH_P_8021AD in this case) is stripped when skb is sent out of netdev.
    
      Also, if NSH is encapsulated by NSH + Ethernet (so NSH-Ethernet-NSH),
      skb_pull() in the first nsh_gso_segment() will make skb->data point
      to the middle of the outer NSH or Ethernet header because the Ethernet
      header is not pulled by the second nsh_gso_segment().
    
      (b)
      While restoring skb->{mac_header,network_header} in 8 & 9,
      nsh_gso_segment() does not assume that the data in the linear
      buffer is shifted.
    
      However, udp6_ufo_fragment() could shift the data and change
      skb->mac_header accordingly as demonstrated by syzbot.
    
      If this happens, even the restored skb->mac_header points to
      the middle of the outer header.
    
    It seems nsh_gso_segment() has never worked with outer headers so far.
    
    At the end of nsh_gso_segment(), the outer header must be restored for
    the segmented skb, instead of the NSH header.
    
    To do that, let's calculate the outer header position relatively from
    the inner header and set skb->{data,mac_header,protocol} properly.
    
    [0]:
    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
    
    Fixes: c411ed854584 ("nsh: add GSO support")
    Reported-and-tested-by: syzbot+42a0dc856239de4de60e@xxxxxxxxxxxxxxxxxxxxxxxxx
    Closes: https://syzkaller.appspot.com/bug?extid=42a0dc856239de4de60e
    Reported-and-tested-by: syzbot+c298c9f0e46a3c86332b@xxxxxxxxxxxxxxxxxxxxxxxxx
    Closes: https://syzkaller.appspot.com/bug?extid=c298c9f0e46a3c86332b
    Link: https://lore.kernel.org/netdev/20240415222041.18537-1-kuniyu@xxxxxxxxxx/
    Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240424023549.21862-1-kuniyu@xxxxxxxxxx
    Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/nsh/nsh.c b/net/nsh/nsh.c
index f4a38bd6a7e04..bfb7758063f31 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 outer_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 outer_proto, proto;
 
 	skb_reset_network_header(skb);
 
+	outer_proto = skb->protocol;
+	outer_hlen = skb_mac_header_len(skb);
 	mac_len = skb->mac_len;
 
 	if (unlikely(!pskb_may_pull(skb, NSH_BASE_HDR_LEN)))
@@ -113,10 +115,10 @@ 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->protocol = outer_proto;
+		__skb_push(skb, nsh_len + outer_hlen);
+		skb_reset_mac_header(skb);
+		skb_set_network_header(skb, outer_hlen);
 		skb->mac_len = mac_len;
 	}
 




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