linux.git/net/ipv6, branch v4.14.217 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git net: ipv6: Validate GSO SKB before finish IPv6 processing 2021-01-23T14:48:48+00:00 Aya Levin ayal@nvidia.com 2021-01-07T13:50:18+00:00 26e5eadac624ca16134c28095026885f7b7b8afa [ Upstream commit b210de4f8c97d57de051e805686248ec4c6cfc52 ] There are cases where GSO segment's length exceeds the egress MTU: - Forwarding of a TCP GRO skb, when DF flag is not set. - Forwarding of an skb that arrived on a virtualisation interface (virtio-net/vhost/tap) with TSO/GSO size set by other network stack. - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an interface with a smaller MTU. - Arriving GRO skb (or GSO skb in a virtualised environment) that is bridged to a NETIF_F_TSO tunnel stacked over an interface with an insufficient MTU. If so: - Consume the SKB and its segments. - Issue an ICMP packet with 'Packet Too Big' message containing the MTU, allowing the source host to reduce its Path MTU appropriately. Note: These cases are handled in the same manner in IPv4 output finish. This patch aligns the behavior of IPv6 and the one of IPv4. Fixes: 9e50849054a4 ("netfilter: ipv6: move POSTROUTING invocation before fragmentation") Signed-off-by: Aya Levin <ayal@nvidia.com> Reviewed-by: Tariq Toukan <tariqt@nvidia.com> Link: https://lore.kernel.org/r/1610027418-30438-1-git-send-email-ayal@nvidia.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit b210de4f8c97d57de051e805686248ec4c6cfc52 ]

There are cases where GSO segment's length exceeds the egress MTU:
 - Forwarding of a TCP GRO skb, when DF flag is not set.
 - Forwarding of an skb that arrived on a virtualisation interface
   (virtio-net/vhost/tap) with TSO/GSO size set by other network
   stack.
 - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an
   interface with a smaller MTU.
 - Arriving GRO skb (or GSO skb in a virtualised environment) that is
   bridged to a NETIF_F_TSO tunnel stacked over an interface with an
   insufficient MTU.

If so:
 - Consume the SKB and its segments.
 - Issue an ICMP packet with 'Packet Too Big' message containing the
   MTU, allowing the source host to reduce its Path MTU appropriately.

Note: These cases are handled in the same manner in IPv4 output finish.
This patch aligns the behavior of IPv6 and the one of IPv4.

Fixes: 9e50849054a4 ("netfilter: ipv6: move POSTROUTING invocation before fragmentation")
Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/1610027418-30438-1-git-send-email-ayal@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net: sit: unregister_netdevice on newlink's error path 2021-01-23T14:48:46+00:00 Jakub Kicinski kuba@kernel.org 2021-01-14T01:29:47+00:00 86fff7c7d4011c4dcea7c68b829db142ef6c938b [ Upstream commit 47e4bb147a96f1c9b4e7691e7e994e53838bfff8 ] We need to unregister the netdevice if config failed. .ndo_uninit takes care of most of the heavy lifting. This was uncovered by recent commit c269a24ce057 ("net: make free_netdev() more lenient with unregistering devices"). Previously the partially-initialized device would be left in the system. Reported-and-tested-by: syzbot+2393580080a2da190f04@syzkaller.appspotmail.com Fixes: e2f1f072db8d ("sit: allow to configure 6rd tunnels via netlink") Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Link: https://lore.kernel.org/r/20210114012947.2515313-1-kuba@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit 47e4bb147a96f1c9b4e7691e7e994e53838bfff8 ]

We need to unregister the netdevice if config failed.
.ndo_uninit takes care of most of the heavy lifting.

This was uncovered by recent commit c269a24ce057 ("net: make
free_netdev() more lenient with unregistering devices").
Previously the partially-initialized device would be left
in the system.

Reported-and-tested-by: syzbot+2393580080a2da190f04@syzkaller.appspotmail.com
Fixes: e2f1f072db8d ("sit: allow to configure 6rd tunnels via netlink")
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Link: https://lore.kernel.org/r/20210114012947.2515313-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
esp: avoid unneeded kmap_atomic call 2021-01-23T14:48:46+00:00 Willem de Bruijn willemb@google.com 2021-01-09T22:18:34+00:00 a9c167459fc87f0e28737696bdc15345038c6063 [ Upstream commit 9bd6b629c39e3fa9e14243a6d8820492be1a5b2e ] esp(6)_output_head uses skb_page_frag_refill to allocate a buffer for the esp trailer. It accesses the page with kmap_atomic to handle highmem. But skb_page_frag_refill can return compound pages, of which kmap_atomic only maps the first underlying page. skb_page_frag_refill does not return highmem, because flag __GFP_HIGHMEM is not set. ESP uses it in the same manner as TCP. That also does not call kmap_atomic, but directly uses page_address, in skb_copy_to_page_nocache. Do the same for ESP. This issue has become easier to trigger with recent kmap local debugging feature CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP. Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible") Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible") Signed-off-by: Willem de Bruijn <willemb@google.com> Acked-by: Steffen Klassert <steffen.klassert@secunet.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit 9bd6b629c39e3fa9e14243a6d8820492be1a5b2e ]

esp(6)_output_head uses skb_page_frag_refill to allocate a buffer for
the esp trailer.

It accesses the page with kmap_atomic to handle highmem. But
skb_page_frag_refill can return compound pages, of which
kmap_atomic only maps the first underlying page.

skb_page_frag_refill does not return highmem, because flag
__GFP_HIGHMEM is not set. ESP uses it in the same manner as TCP.
That also does not call kmap_atomic, but directly uses page_address,
in skb_copy_to_page_nocache. Do the same for ESP.

This issue has become easier to trigger with recent kmap local
debugging feature CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP.

Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
Fixes: 03e2a30f6a27 ("esp6: Avoid skb_cow_data whenever possible")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ah6: fix error return code in ah6_input() 2020-11-24T12:05:35+00:00 Zhang Changzhong zhangchangzhong@huawei.com 2020-11-17T02:45:05+00:00 47bd21ab07b3e3ac4088a714d99189783dc67377 [ Upstream commit a5ebcbdf34b65fcc07f38eaf2d60563b42619a59 ] Fix to return a negative error code from the error handling case instead of 0, as done elsewhere in this function. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com> Link: https://lore.kernel.org/r/1605581105-35295-1-git-send-email-zhangchangzhong@huawei.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit a5ebcbdf34b65fcc07f38eaf2d60563b42619a59 ]

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Link: https://lore.kernel.org/r/1605581105-35295-1-git-send-email-zhangchangzhong@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net: Update window_clamp if SOCK_RCVBUF is set 2020-11-18T17:28:00+00:00 Mao Wenan wenan.mao@linux.alibaba.com 2020-11-10T00:16:31+00:00 fc08b8e9d8928a21faf7fb5d31fc5d3f26a910a8 [ Upstream commit 909172a149749242990a6e64cb55d55460d4e417 ] When net.ipv4.tcp_syncookies=1 and syn flood is happened, cookie_v4_check or cookie_v6_check tries to redo what tcp_v4_send_synack or tcp_v6_send_synack did, rsk_window_clamp will be changed if SOCK_RCVBUF is set, which will make rcv_wscale is different, the client still operates with initial window scale and can overshot granted window, the client use the initial scale but local server use new scale to advertise window value, and session work abnormally. Fixes: e88c64f0a425 ("tcp: allow effective reduction of TCP's rcv-buffer via setsockopt") Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Link: https://lore.kernel.org/r/1604967391-123737-1-git-send-email-wenan.mao@linux.alibaba.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit 909172a149749242990a6e64cb55d55460d4e417 ]

When net.ipv4.tcp_syncookies=1 and syn flood is happened,
cookie_v4_check or cookie_v6_check tries to redo what
tcp_v4_send_synack or tcp_v6_send_synack did,
rsk_window_clamp will be changed if SOCK_RCVBUF is set,
which will make rcv_wscale is different, the client
still operates with initial window scale and can overshot
granted window, the client use the initial scale but local
server use new scale to advertise window value, and session
work abnormally.

Fixes: e88c64f0a425 ("tcp: allow effective reduction of TCP's rcv-buffer via setsockopt")
Signed-off-by: Mao Wenan <wenan.mao@linux.alibaba.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/1604967391-123737-1-git-send-email-wenan.mao@linux.alibaba.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
IPv6: Set SIT tunnel hard_header_len to zero 2020-11-18T17:27:59+00:00 Oliver Herms oliver.peter.herms@gmail.com 2020-11-03T10:41:33+00:00 631d8475dfb197140a8501f8079e8a8ae4f0638c [ Upstream commit 8ef9ba4d666614497a057d09b0a6eafc1e34eadf ] Due to the legacy usage of hard_header_len for SIT tunnels while already using infrastructure from net/ipv4/ip_tunnel.c the calculation of the path MTU in tnl_update_pmtu is incorrect. This leads to unnecessary creation of MTU exceptions for any flow going over a SIT tunnel. As SIT tunnels do not have a header themsevles other than their transport (L3, L2) headers we're leaving hard_header_len set to zero as tnl_update_pmtu is already taking care of the transport headers sizes. This will also help avoiding unnecessary IPv6 GC runs and spinlock contention seen when using SIT tunnels and for more than net.ipv6.route.gc_thresh flows. Fixes: c54419321455 ("GRE: Refactor GRE tunneling code.") Signed-off-by: Oliver Herms <oliver.peter.herms@gmail.com> Acked-by: Willem de Bruijn <willemb@google.com> Link: https://lore.kernel.org/r/20201103104133.GA1573211@tws Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit 8ef9ba4d666614497a057d09b0a6eafc1e34eadf ]

Due to the legacy usage of hard_header_len for SIT tunnels while
already using infrastructure from net/ipv4/ip_tunnel.c the
calculation of the path MTU in tnl_update_pmtu is incorrect.
This leads to unnecessary creation of MTU exceptions for any
flow going over a SIT tunnel.

As SIT tunnels do not have a header themsevles other than their
transport (L3, L2) headers we're leaving hard_header_len set to zero
as tnl_update_pmtu is already taking care of the transport headers
sizes.

This will also help avoiding unnecessary IPv6 GC runs and spinlock
contention seen when using SIT tunnels and for more than
net.ipv6.route.gc_thresh flows.

Fixes: c54419321455 ("GRE: Refactor GRE tunneling code.")
Signed-off-by: Oliver Herms <oliver.peter.herms@gmail.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20201103104133.GA1573211@tws
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net: ipv6: fix kconfig dependency warning for IPV6_SEG6_HMAC 2020-10-01T11:12:24+00:00 Necip Fazil Yildiran fazilyildiran@gmail.com 2020-09-17T16:46:43+00:00 be619e3cbe46b8276b3f75d86e4d4055d55f9471 [ Upstream commit db7cd91a4be15e1485d6b58c6afc8761c59c4efb ] When IPV6_SEG6_HMAC is enabled and CRYPTO is disabled, it results in the following Kbuild warning: WARNING: unmet direct dependencies detected for CRYPTO_HMAC Depends on [n]: CRYPTO [=n] Selected by [y]: - IPV6_SEG6_HMAC [=y] && NET [=y] && INET [=y] && IPV6 [=y] WARNING: unmet direct dependencies detected for CRYPTO_SHA1 Depends on [n]: CRYPTO [=n] Selected by [y]: - IPV6_SEG6_HMAC [=y] && NET [=y] && INET [=y] && IPV6 [=y] WARNING: unmet direct dependencies detected for CRYPTO_SHA256 Depends on [n]: CRYPTO [=n] Selected by [y]: - IPV6_SEG6_HMAC [=y] && NET [=y] && INET [=y] && IPV6 [=y] The reason is that IPV6_SEG6_HMAC selects CRYPTO_HMAC, CRYPTO_SHA1, and CRYPTO_SHA256 without depending on or selecting CRYPTO while those configs are subordinate to CRYPTO. Honor the kconfig menu hierarchy to remove kconfig dependency warnings. Fixes: bf355b8d2c30 ("ipv6: sr: add core files for SR HMAC support") Signed-off-by: Necip Fazil Yildiran <fazilyildiran@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit db7cd91a4be15e1485d6b58c6afc8761c59c4efb ]

When IPV6_SEG6_HMAC is enabled and CRYPTO is disabled, it results in the
following Kbuild warning:

WARNING: unmet direct dependencies detected for CRYPTO_HMAC
  Depends on [n]: CRYPTO [=n]
  Selected by [y]:
  - IPV6_SEG6_HMAC [=y] && NET [=y] && INET [=y] && IPV6 [=y]

WARNING: unmet direct dependencies detected for CRYPTO_SHA1
  Depends on [n]: CRYPTO [=n]
  Selected by [y]:
  - IPV6_SEG6_HMAC [=y] && NET [=y] && INET [=y] && IPV6 [=y]

WARNING: unmet direct dependencies detected for CRYPTO_SHA256
  Depends on [n]: CRYPTO [=n]
  Selected by [y]:
  - IPV6_SEG6_HMAC [=y] && NET [=y] && INET [=y] && IPV6 [=y]

The reason is that IPV6_SEG6_HMAC selects CRYPTO_HMAC, CRYPTO_SHA1, and
CRYPTO_SHA256 without depending on or selecting CRYPTO while those configs
are subordinate to CRYPTO.

Honor the kconfig menu hierarchy to remove kconfig dependency warnings.

Fixes: bf355b8d2c30 ("ipv6: sr: add core files for SR HMAC support")
Signed-off-by: Necip Fazil Yildiran <fazilyildiran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
gre6: Fix reception with IP6_TNL_F_RCV_DSCP_COPY 2020-09-03T09:22:24+00:00 Mark Tomlinson mark.tomlinson@alliedtelesis.co.nz 2020-08-19T01:53:58+00:00 70154c4f30dd0f61f9496483620e872c2b6e9f4f [ Upstream commit 272502fcb7cda01ab07fc2fcff82d1d2f73d43cc ] When receiving an IPv4 packet inside an IPv6 GRE packet, and the IP6_TNL_F_RCV_DSCP_COPY flag is set on the tunnel, the IPv4 header would get corrupted. This is due to the common ip6_tnl_rcv() function assuming that the inner header is always IPv6. This patch checks the tunnel protocol for IPv4 inner packets, but still defaults to IPv6. Fixes: 308edfdf1563 ("gre6: Cleanup GREv6 receive path, call common GRE functions") Signed-off-by: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit 272502fcb7cda01ab07fc2fcff82d1d2f73d43cc ]

When receiving an IPv4 packet inside an IPv6 GRE packet, and the
IP6_TNL_F_RCV_DSCP_COPY flag is set on the tunnel, the IPv4 header would
get corrupted. This is due to the common ip6_tnl_rcv() function assuming
that the inner header is always IPv6. This patch checks the tunnel
protocol for IPv4 inner packets, but still defaults to IPv6.

Fixes: 308edfdf1563 ("gre6: Cleanup GREv6 receive path, call common GRE functions")
Signed-off-by: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ipv6: fix memory leaks on IPV6_ADDRFORM path 2020-08-21T07:48:00+00:00 Cong Wang xiyou.wangcong@gmail.com 2020-07-25T22:40:53+00:00 da34873e8fb08a306de0c95457de1f63690114ce [ Upstream commit 8c0de6e96c9794cb523a516c465991a70245da1c ] IPV6_ADDRFORM causes resource leaks when converting an IPv6 socket to IPv4, particularly struct ipv6_ac_socklist. Similar to struct ipv6_mc_socklist, we should just close it on this path. This bug can be easily reproduced with the following C program: #include <stdio.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> int main() { int s, value; struct sockaddr_in6 addr; struct ipv6_mreq m6; s = socket(AF_INET6, SOCK_DGRAM, 0); addr.sin6_family = AF_INET6; addr.sin6_port = htons(5000); inet_pton(AF_INET6, "::ffff:192.168.122.194", &addr.sin6_addr); connect(s, (struct sockaddr *)&addr, sizeof(addr)); inet_pton(AF_INET6, "fe80::AAAA", &m6.ipv6mr_multiaddr); m6.ipv6mr_interface = 5; setsockopt(s, SOL_IPV6, IPV6_JOIN_ANYCAST, &m6, sizeof(m6)); value = AF_INET; setsockopt(s, SOL_IPV6, IPV6_ADDRFORM, &value, sizeof(value)); close(s); return 0; } Reported-by: ch3332xr@gmail.com Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit 8c0de6e96c9794cb523a516c465991a70245da1c ]

IPV6_ADDRFORM causes resource leaks when converting an IPv6 socket
to IPv4, particularly struct ipv6_ac_socklist. Similar to
struct ipv6_mc_socklist, we should just close it on this path.

This bug can be easily reproduced with the following C program:

  #include <stdio.h>
  #include <string.h>
  #include <sys/types.h>
  #include <sys/socket.h>
  #include <arpa/inet.h>

  int main()
  {
    int s, value;
    struct sockaddr_in6 addr;
    struct ipv6_mreq m6;

    s = socket(AF_INET6, SOCK_DGRAM, 0);
    addr.sin6_family = AF_INET6;
    addr.sin6_port = htons(5000);
    inet_pton(AF_INET6, "::ffff:192.168.122.194", &addr.sin6_addr);
    connect(s, (struct sockaddr *)&addr, sizeof(addr));

    inet_pton(AF_INET6, "fe80::AAAA", &m6.ipv6mr_multiaddr);
    m6.ipv6mr_interface = 5;
    setsockopt(s, SOL_IPV6, IPV6_JOIN_ANYCAST, &m6, sizeof(m6));

    value = AF_INET;
    setsockopt(s, SOL_IPV6, IPV6_ADDRFORM, &value, sizeof(value));

    close(s);
    return 0;
  }

Reported-by: ch3332xr@gmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ip6_gre: fix null-ptr-deref in ip6gre_init_net() 2020-07-31T14:44:44+00:00 Wei Yongjun weiyongjun1@huawei.com 2020-07-13T15:59:50+00:00 d6b1ffe225b2524c70d2be829a412da0eda66f84 [ Upstream commit 46ef5b89ec0ecf290d74c4aee844f063933c4da4 ] KASAN report null-ptr-deref error when register_netdev() failed: KASAN: null-ptr-deref in range [0x00000000000003c0-0x00000000000003c7] CPU: 2 PID: 422 Comm: ip Not tainted 5.8.0-rc4+ #12 Call Trace: ip6gre_init_net+0x4ab/0x580 ? ip6gre_tunnel_uninit+0x3f0/0x3f0 ops_init+0xa8/0x3c0 setup_net+0x2de/0x7e0 ? rcu_read_lock_bh_held+0xb0/0xb0 ? ops_init+0x3c0/0x3c0 ? kasan_unpoison_shadow+0x33/0x40 ? __kasan_kmalloc.constprop.0+0xc2/0xd0 copy_net_ns+0x27d/0x530 create_new_namespaces+0x382/0xa30 unshare_nsproxy_namespaces+0xa1/0x1d0 ksys_unshare+0x39c/0x780 ? walk_process_tree+0x2a0/0x2a0 ? trace_hardirqs_on+0x4a/0x1b0 ? _raw_spin_unlock_irq+0x1f/0x30 ? syscall_trace_enter+0x1a7/0x330 ? do_syscall_64+0x1c/0xa0 __x64_sys_unshare+0x2d/0x40 do_syscall_64+0x56/0xa0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 ip6gre_tunnel_uninit() has set 'ign->fb_tunnel_dev' to NULL, later access to ign->fb_tunnel_dev cause null-ptr-deref. Fix it by saving 'ign->fb_tunnel_dev' to local variable ndev. Fixes: dafabb6590cb ("ip6_gre: fix use-after-free in ip6gre_tunnel_lookup()") Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit 46ef5b89ec0ecf290d74c4aee844f063933c4da4 ]

KASAN report null-ptr-deref error when register_netdev() failed:

KASAN: null-ptr-deref in range [0x00000000000003c0-0x00000000000003c7]
CPU: 2 PID: 422 Comm: ip Not tainted 5.8.0-rc4+ #12
Call Trace:
 ip6gre_init_net+0x4ab/0x580
 ? ip6gre_tunnel_uninit+0x3f0/0x3f0
 ops_init+0xa8/0x3c0
 setup_net+0x2de/0x7e0
 ? rcu_read_lock_bh_held+0xb0/0xb0
 ? ops_init+0x3c0/0x3c0
 ? kasan_unpoison_shadow+0x33/0x40
 ? __kasan_kmalloc.constprop.0+0xc2/0xd0
 copy_net_ns+0x27d/0x530
 create_new_namespaces+0x382/0xa30
 unshare_nsproxy_namespaces+0xa1/0x1d0
 ksys_unshare+0x39c/0x780
 ? walk_process_tree+0x2a0/0x2a0
 ? trace_hardirqs_on+0x4a/0x1b0
 ? _raw_spin_unlock_irq+0x1f/0x30
 ? syscall_trace_enter+0x1a7/0x330
 ? do_syscall_64+0x1c/0xa0
 __x64_sys_unshare+0x2d/0x40
 do_syscall_64+0x56/0xa0
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

ip6gre_tunnel_uninit() has set 'ign->fb_tunnel_dev' to NULL, later
access to ign->fb_tunnel_dev cause null-ptr-deref. Fix it by saving
'ign->fb_tunnel_dev' to local variable ndev.

Fixes: dafabb6590cb ("ip6_gre: fix use-after-free in ip6gre_tunnel_lookup()")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>