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Date: Tue, 27 Sep 2022 09:55:03 -0700 From: Eric Dumazet <edumazet@...gle.com> To: Kuniyuki Iwashima <kuniyu@...zon.com> Cc: David Miller <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, Jakub Kicinski <kuba@...nel.org>, Kuniyuki Iwashima <kuni1840@...il.com>, LKML <linux-kernel@...r.kernel.org>, netdev <netdev@...r.kernel.org>, Paolo Abeni <pabeni@...hat.com>, syzkaller-bugs <syzkaller-bugs@...glegroups.com> Subject: Re: [PATCH v1 net 5/5] tcp: Fix data races around icsk->icsk_af_ops. On Tue, Sep 27, 2022 at 9:48 AM Kuniyuki Iwashima <kuniyu@...zon.com> wrote: > > From: Eric Dumazet <edumazet@...gle.com> > Date: Tue, 27 Sep 2022 09:39:37 -0700 > > On Tue, Sep 27, 2022 at 9:33 AM Kuniyuki Iwashima <kuniyu@...zon.com> wrote: > > > > > > IPV6_ADDRFORM changes icsk->icsk_af_ops under lock_sock(), but > > > tcp_(get|set)sockopt() read it locklessly. To avoid load/store > > > tearing, we need to add READ_ONCE() and WRITE_ONCE() for the reads > > > and write. > > > > I am pretty sure I have released a syzkaller bug recently with this issue. > > Have you seen this? > > If yes, please include the appropriate syzbot tag. > > No, I haven't. > Could you provide the URL? > I'm happy to include the syzbot tag and KCSAN report in the changelog. > > Report has been released 10 days ago, but apparently the syzbot queue is so full these days that the report is still throttled. ================================================================== BUG: KCSAN: data-race in tcp_setsockopt / tcp_v6_connect write to 0xffff88813c624518 of 8 bytes by task 23936 on cpu 0: tcp_v6_connect+0x5b3/0xce0 net/ipv6/tcp_ipv6.c:240 __inet_stream_connect+0x159/0x6d0 net/ipv4/af_inet.c:660 inet_stream_connect+0x44/0x70 net/ipv4/af_inet.c:724 __sys_connect_file net/socket.c:1976 [inline] __sys_connect+0x197/0x1b0 net/socket.c:1993 __do_sys_connect net/socket.c:2003 [inline] __se_sys_connect net/socket.c:2000 [inline] __x64_sys_connect+0x3d/0x50 net/socket.c:2000 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd read to 0xffff88813c624518 of 8 bytes by task 23937 on cpu 1: tcp_setsockopt+0x147/0x1c80 net/ipv4/tcp.c:3789 sock_common_setsockopt+0x5d/0x70 net/core/sock.c:3585 __sys_setsockopt+0x212/0x2b0 net/socket.c:2252 __do_sys_setsockopt net/socket.c:2263 [inline] __se_sys_setsockopt net/socket.c:2260 [inline] __x64_sys_setsockopt+0x62/0x70 net/socket.c:2260 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd value changed: 0xffffffff8539af68 -> 0xffffffff8539aff8 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 23937 Comm: syz-executor.5 Not tainted 6.0.0-rc4-syzkaller-00331-g4ed9c1e971b1-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022 ================================================================== > > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > > > Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com> > > > --- > > > net/ipv4/tcp.c | 10 ++++++---- > > > net/ipv6/ipv6_sockglue.c | 3 ++- > > > 2 files changed, 8 insertions(+), 5 deletions(-) > > > > > > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c > > > index e373dde1f46f..c86dd0ccef5b 100644 > > > --- a/net/ipv4/tcp.c > > > +++ b/net/ipv4/tcp.c > > > @@ -3795,8 +3795,9 @@ int tcp_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval, > > > const struct inet_connection_sock *icsk = inet_csk(sk); > > > > > > if (level != SOL_TCP) > > > - return icsk->icsk_af_ops->setsockopt(sk, level, optname, > > > - optval, optlen); > > > + /* IPV6_ADDRFORM can change icsk->icsk_af_ops under us. */ > > > + return READ_ONCE(icsk->icsk_af_ops)->setsockopt(sk, level, optname, > > > + optval, optlen); > > > return do_tcp_setsockopt(sk, level, optname, optval, optlen); > > > } > > > EXPORT_SYMBOL(tcp_setsockopt); > > > @@ -4394,8 +4395,9 @@ int tcp_getsockopt(struct sock *sk, int level, int optname, char __user *optval, > > > struct inet_connection_sock *icsk = inet_csk(sk); > > > > > > if (level != SOL_TCP) > > > - return icsk->icsk_af_ops->getsockopt(sk, level, optname, > > > - optval, optlen); > > > + /* IPV6_ADDRFORM can change icsk->icsk_af_ops under us. */ > > > + return READ_ONCE(icsk->icsk_af_ops)->getsockopt(sk, level, optname, > > > + optval, optlen); > > > return do_tcp_getsockopt(sk, level, optname, optval, optlen); > > > } > > > EXPORT_SYMBOL(tcp_getsockopt); > > > diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c > > > index a89db5872dc3..726d95859898 100644 > > > --- a/net/ipv6/ipv6_sockglue.c > > > +++ b/net/ipv6/ipv6_sockglue.c > > > @@ -479,7 +479,8 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname, > > > > > > /* Paired with READ_ONCE(sk->sk_prot) in inet6_stream_ops */ > > > WRITE_ONCE(sk->sk_prot, &tcp_prot); > > > - icsk->icsk_af_ops = &ipv4_specific; > > > + /* Paired with READ_ONCE() in tcp_(get|set)sockopt() */ > > > + WRITE_ONCE(icsk->icsk_af_ops, &ipv4_specific); > > > sk->sk_socket->ops = &inet_stream_ops; > > > sk->sk_family = PF_INET; > > > tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); > > > -- > > > 2.30.2 > > >
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