netdev - Re: [PATCH net] sctp: initialize more fields in sctp_v6_from

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Message-ID: <CADvbK_eG+f4O+WGBFucpWTZFvpPxWJ6obnV8hHPsX1RvEonWDw@mail.gmail.com>
Date: Tue, 26 Aug 2025 10:29:34 -0400
From: Xin Long <lucien.xin@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, syzbot+e69f06a0f30116c68056@...kaller.appspotmail.com, 
	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net] sctp: initialize more fields in sctp_v6_from_sk()

On Tue, Aug 26, 2025 at 10:13 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> syzbot found that sin6_scope_id was not properly initialized,
> leading to undefined behavior.
>
> Clear sin6_scope_id and sin6_flowinfo.
>
> BUG: KMSAN: uninit-value in __sctp_v6_cmp_addr+0x887/0x8c0 net/sctp/ipv6.c:649
>   __sctp_v6_cmp_addr+0x887/0x8c0 net/sctp/ipv6.c:649
>   sctp_inet6_cmp_addr+0x4f2/0x510 net/sctp/ipv6.c:983
>   sctp_bind_addr_conflict+0x22a/0x3b0 net/sctp/bind_addr.c:390
>   sctp_get_port_local+0x21eb/0x2440 net/sctp/socket.c:8452
>   sctp_get_port net/sctp/socket.c:8523 [inline]
>   sctp_listen_start net/sctp/socket.c:8567 [inline]
>   sctp_inet_listen+0x710/0xfd0 net/sctp/socket.c:8636
>   __sys_listen_socket net/socket.c:1912 [inline]
>   __sys_listen net/socket.c:1927 [inline]
>   __do_sys_listen net/socket.c:1932 [inline]
>   __se_sys_listen net/socket.c:1930 [inline]
>   __x64_sys_listen+0x343/0x4c0 net/socket.c:1930
>   x64_sys_call+0x271d/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:51
>   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>   do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Local variable addr.i.i created at:
>   sctp_get_port net/sctp/socket.c:8515 [inline]
>   sctp_listen_start net/sctp/socket.c:8567 [inline]
>   sctp_inet_listen+0x650/0xfd0 net/sctp/socket.c:8636
>   __sys_listen_socket net/socket.c:1912 [inline]
>   __sys_listen net/socket.c:1927 [inline]
>   __do_sys_listen net/socket.c:1932 [inline]
>   __se_sys_listen net/socket.c:1930 [inline]
>   __x64_sys_listen+0x343/0x4c0 net/socket.c:1930
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: syzbot+e69f06a0f30116c68056@...kaller.appspotmail.com
> Closes: https://lore.kernel.org/netdev/68adc0a2.050a0220.37038e.00c4.GAE@google.com/T/#u
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> Cc: Xin Long <lucien.xin@...il.com>
> ---
>  net/sctp/ipv6.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
> index 3336dcfb451509927a4ae3c2bf76c574c743936b..568ff8797c393bea28f8423babd4c85d6407f9ff 100644
> --- a/net/sctp/ipv6.c
> +++ b/net/sctp/ipv6.c
> @@ -547,7 +547,9 @@ static void sctp_v6_from_sk(union sctp_addr *addr, struct sock *sk)
>  {
>         addr->v6.sin6_family = AF_INET6;
>         addr->v6.sin6_port = 0;
> +       addr->v6.sin6_flowinfo = 0;
>         addr->v6.sin6_addr = sk->sk_v6_rcv_saddr;
> +       addr->v6.sin6_scope_id = 0;
>  }
>
>  /* Initialize sk->sk_rcv_saddr from sctp_addr. */
> --
> 2.51.0.261.g7ce5a0a67e-goog
>
Acked-by: Xin Long <lucien.xin@...il.com>

Thanks.