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syzbot was able to crash one host with the following stack trace : kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 8625 Comm: syz-executor4 Not tainted 4.20.0+ #8 RIP: 0010:dev_net include/linux/netdevice.h:2169 [inline] RIP: 0010:icmp6_send+0x116/0x2d30 net/ipv6/icmp.c:426 icmpv6_send smack_socket_sock_rcv_skb security_sock_rcv_skb sk_filter_trim_cap __sk_receive_skb dccp_v6_do_rcv release_sock This is because a RX packet found socket owned by user and was stored into socket backlog. Before leaving RCU protected section, skb->dev was cleared in __sk_receive_skb(). When socket backlog was finally handled at release_sock() time, skb was fed to smack_socket_sock_rcv_skb() then icmp6_send() We could fix the bug in smack_socket_sock_rcv_skb(), or simply make icmp6_send() more robust against such possibility. In the future we might provide to icmp6_send() the net pointer instead of infering it. Fixes: d66a8acbda92 ("Smack: Inform peer that IPv6 traffic has been blocked") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Piotr Sawicki <p.sawicki2@partner.samsung.com> Cc: Casey Schaufler <casey@schaufler-ca.com> Reported-by: syzbot <syzkaller@googlegroups.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.