| Message ID | 1210177.1727215681@warthog.procyon.org.uk (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] rxrpc: Fix a race between socket set up and I/O thread creation | expand |
On Tue, Sep 24, 2024 at 11:08:01PM +0100, David Howells wrote: > In rxrpc_open_socket(), it sets up the socket and then sets up the I/O > thread that will handle it. This is a problem, however, as there's a gap > between the two phases in which a packet may come into rxrpc_encap_rcv() > from the UDP packet but we oops when trying to wake the not-yet created I/O > thread. > > As a quick fix, just make rxrpc_encap_rcv() discard the packet if there's > no I/O thread yet. > > A better, but more intrusive fix would perhaps be to rearrange things such > that the socket creation is done by the I/O thread. > > Fixes: a275da62e8c1 ("rxrpc: Create a per-local endpoint receive queue and I/O thread") > Signed-off-by: David Howells <dhowells@redhat.com> > Reviewed-by: Eric Dumazet <edumazet@google.com> ...:wq > diff --git a/net/rxrpc/io_thread.c b/net/rxrpc/io_thread.c > index 0300baa9afcd..5c0a5374d51a 100644 > --- a/net/rxrpc/io_thread.c > +++ b/net/rxrpc/io_thread.c > @@ -27,8 +27,9 @@ int rxrpc_encap_rcv(struct sock *udp_sk, struct sk_buff *skb) > { > struct sk_buff_head *rx_queue; > struct rxrpc_local *local = rcu_dereference_sk_user_data(udp_sk); > + struct task_struct *io_thread = READ_ONCE(local->io_thread); Hi David, The line above dereferences local. But the line below assumes that it may be NULL. This seems inconsistent. Flagged by Smatch. > > - if (unlikely(!local)) { > + if (unlikely(!local || !io_thread)) { > kfree_skb(skb); > return 0; > }
On 9/25/24 20:33, Simon Horman wrote: > On Tue, Sep 24, 2024 at 11:08:01PM +0100, David Howells wrote: >> In rxrpc_open_socket(), it sets up the socket and then sets up the I/O >> thread that will handle it. This is a problem, however, as there's a gap >> between the two phases in which a packet may come into rxrpc_encap_rcv() >> from the UDP packet but we oops when trying to wake the not-yet created I/O >> thread. >> >> As a quick fix, just make rxrpc_encap_rcv() discard the packet if there's >> no I/O thread yet. >> >> A better, but more intrusive fix would perhaps be to rearrange things such >> that the socket creation is done by the I/O thread. >> >> Fixes: a275da62e8c1 ("rxrpc: Create a per-local endpoint receive queue and I/O thread") >> Signed-off-by: David Howells <dhowells@redhat.com> >> Reviewed-by: Eric Dumazet <edumazet@google.com> > > ...:wq > >> diff --git a/net/rxrpc/io_thread.c b/net/rxrpc/io_thread.c >> index 0300baa9afcd..5c0a5374d51a 100644 >> --- a/net/rxrpc/io_thread.c >> +++ b/net/rxrpc/io_thread.c >> @@ -27,8 +27,9 @@ int rxrpc_encap_rcv(struct sock *udp_sk, struct sk_buff *skb) >> { >> struct sk_buff_head *rx_queue; >> struct rxrpc_local *local = rcu_dereference_sk_user_data(udp_sk); >> + struct task_struct *io_thread = READ_ONCE(local->io_thread); > > Hi David, > > The line above dereferences local. > But the line below assumes that it may be NULL. > This seems inconsistent. sk->sk_user_data is cleared just before io_thread by rxrpc_io_thread(), I think accessing a NULL 'local' here should be possible. @David, could you please respin addressing the above? Thanks! Paolo
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h index 80d682f89b23..d0fd37bdcfe9 100644 --- a/net/rxrpc/ar-internal.h +++ b/net/rxrpc/ar-internal.h @@ -1056,7 +1056,7 @@ bool rxrpc_direct_abort(struct sk_buff *skb, enum rxrpc_abort_reason why, int rxrpc_io_thread(void *data); static inline void rxrpc_wake_up_io_thread(struct rxrpc_local *local) { - wake_up_process(local->io_thread); + wake_up_process(READ_ONCE(local->io_thread)); } static inline bool rxrpc_protocol_error(struct sk_buff *skb, enum rxrpc_abort_reason why) diff --git a/net/rxrpc/io_thread.c b/net/rxrpc/io_thread.c index 0300baa9afcd..5c0a5374d51a 100644 --- a/net/rxrpc/io_thread.c +++ b/net/rxrpc/io_thread.c @@ -27,8 +27,9 @@ int rxrpc_encap_rcv(struct sock *udp_sk, struct sk_buff *skb) { struct sk_buff_head *rx_queue; struct rxrpc_local *local = rcu_dereference_sk_user_data(udp_sk); + struct task_struct *io_thread = READ_ONCE(local->io_thread); - if (unlikely(!local)) { + if (unlikely(!local || !io_thread)) { kfree_skb(skb); return 0; } @@ -47,7 +48,7 @@ int rxrpc_encap_rcv(struct sock *udp_sk, struct sk_buff *skb) #endif skb_queue_tail(rx_queue, skb); - rxrpc_wake_up_io_thread(local); + wake_up_process(io_thread); return 0; } @@ -565,7 +566,7 @@ int rxrpc_io_thread(void *data) __set_current_state(TASK_RUNNING); rxrpc_see_local(local, rxrpc_local_stop); rxrpc_destroy_local(local); - local->io_thread = NULL; + WRITE_ONCE(local->io_thread, NULL); rxrpc_see_local(local, rxrpc_local_stopped); return 0; } diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c index 504453c688d7..f9623ace2201 100644 --- a/net/rxrpc/local_object.c +++ b/net/rxrpc/local_object.c @@ -232,7 +232,7 @@ static int rxrpc_open_socket(struct rxrpc_local *local, struct net *net) } wait_for_completion(&local->io_thread_ready); - local->io_thread = io_thread; + WRITE_ONCE(local->io_thread, io_thread); _leave(" = 0"); return 0;
In rxrpc_open_socket(), it sets up the socket and then sets up the I/O thread that will handle it. This is a problem, however, as there's a gap between the two phases in which a packet may come into rxrpc_encap_rcv() from the UDP packet but we oops when trying to wake the not-yet created I/O thread. As a quick fix, just make rxrpc_encap_rcv() discard the packet if there's no I/O thread yet. A better, but more intrusive fix would perhaps be to rearrange things such that the socket creation is done by the I/O thread. Fixes: a275da62e8c1 ("rxrpc: Create a per-local endpoint receive queue and I/O thread") Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Eric Dumazet <edumazet@google.com> cc: yuxuanzhe@outlook.com cc: Marc Dionne <marc.dionne@auristor.com> cc: "David S. Miller" <davem@davemloft.net> cc: Jakub Kicinski <kuba@kernel.org> cc: Paolo Abeni <pabeni@redhat.com> cc: linux-afs@lists.infradead.org cc: netdev@vger.kernel.org --- net/rxrpc/ar-internal.h | 2 +- net/rxrpc/io_thread.c | 7 ++++--- net/rxrpc/local_object.c | 2 +- 3 files changed, 6 insertions(+), 5 deletions(-)