* [PATCH] SUNRPC: fix race to sk_err after xs_error_report
@ 2019-10-01 18:30 Benjamin Coddington
2019-10-01 19:38 ` Trond Myklebust
0 siblings, 1 reply; 3+ messages in thread
From: Benjamin Coddington @ 2019-10-01 18:30 UTC (permalink / raw)
To: Trond Myklebust, Anna Schumaker; +Cc: James Harvey, linux-nfs
Since commit 4f8943f80883 ("SUNRPC: Replace direct task wakeups from
softirq context") there has been a race to the value of the sk_err if both
XPRT_SOCK_WAKE_ERROR and XPRT_SOCK_WAKE_DISCONNECT are set. In that case,
we may end up losing the sk_err value that existed when xs_error_report was
called.
Fix this by reverting to the previous behavior: instead of using SO_ERROR
to retrieve the value at a later time (which might also return sk_err_soft),
copy the sk_err value onto struct sock_xprt, and use that value to wake
pending tasks.
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Fixes: 4f8943f80883 ("SUNRPC: Replace direct task wakeups from softirq context")
---
include/linux/sunrpc/xprtsock.h | 1 +
net/sunrpc/xprtsock.c | 13 +++++--------
2 files changed, 6 insertions(+), 8 deletions(-)
diff --git a/include/linux/sunrpc/xprtsock.h b/include/linux/sunrpc/xprtsock.h
index 7638dbe7bc50..8ffae73dea6c 100644
--- a/include/linux/sunrpc/xprtsock.h
+++ b/include/linux/sunrpc/xprtsock.h
@@ -56,6 +56,7 @@ struct sock_xprt {
*/
unsigned long sock_state;
struct delayed_work connect_worker;
+ int xprt_err;
struct work_struct error_worker;
struct work_struct recv_worker;
struct mutex recv_mutex;
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index e2176c167a57..7fe77eef7080 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1250,12 +1250,12 @@ static void xs_error_report(struct sock *sk)
goto out;
transport = container_of(xprt, struct sock_xprt, xprt);
- err = -sk->sk_err;
- if (err == 0)
+ transport->xprt_err = -sk->sk_err;
+ if (transport->xprt_err == 0)
goto out;
dprintk("RPC: xs_error_report client %p, error=%d...\n",
- xprt, -err);
- trace_rpc_socket_error(xprt, sk->sk_socket, err);
+ xprt, -transport->xprt_err);
+ trace_rpc_socket_error(xprt, sk->sk_socket, transport->xprt_err);
xs_run_error_worker(transport, XPRT_SOCK_WAKE_ERROR);
out:
read_unlock_bh(&sk->sk_callback_lock);
@@ -2470,7 +2470,6 @@ static void xs_wake_write(struct sock_xprt *transport)
static void xs_wake_error(struct sock_xprt *transport)
{
int sockerr;
- int sockerr_len = sizeof(sockerr);
if (!test_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state))
return;
@@ -2479,9 +2478,7 @@ static void xs_wake_error(struct sock_xprt *transport)
goto out;
if (!test_and_clear_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state))
goto out;
- if (kernel_getsockopt(transport->sock, SOL_SOCKET, SO_ERROR,
- (char *)&sockerr, &sockerr_len) != 0)
- goto out;
+ sockerr = xchg(&transport->xprt_err, 0);
if (sockerr < 0)
xprt_wake_pending_tasks(&transport->xprt, sockerr);
out:
--
2.20.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] SUNRPC: fix race to sk_err after xs_error_report
2019-10-01 18:30 [PATCH] SUNRPC: fix race to sk_err after xs_error_report Benjamin Coddington
@ 2019-10-01 19:38 ` Trond Myklebust
2019-10-02 10:41 ` Benjamin Coddington
0 siblings, 1 reply; 3+ messages in thread
From: Trond Myklebust @ 2019-10-01 19:38 UTC (permalink / raw)
To: bcodding, Anna.Schumaker; +Cc: linux-nfs, jamespharvey20
On Tue, 2019-10-01 at 14:30 -0400, Benjamin Coddington wrote:
> Since commit 4f8943f80883 ("SUNRPC: Replace direct task wakeups from
> softirq context") there has been a race to the value of the sk_err if
> both
> XPRT_SOCK_WAKE_ERROR and XPRT_SOCK_WAKE_DISCONNECT are set. In that
> case,
> we may end up losing the sk_err value that existed when
> xs_error_report was
> called.
>
> Fix this by reverting to the previous behavior: instead of using
> SO_ERROR
> to retrieve the value at a later time (which might also return
> sk_err_soft),
> copy the sk_err value onto struct sock_xprt, and use that value to
> wake
> pending tasks.
>
> Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
> Fixes: 4f8943f80883 ("SUNRPC: Replace direct task wakeups from
> softirq context")
> ---
> include/linux/sunrpc/xprtsock.h | 1 +
> net/sunrpc/xprtsock.c | 13 +++++--------
> 2 files changed, 6 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/sunrpc/xprtsock.h
> b/include/linux/sunrpc/xprtsock.h
> index 7638dbe7bc50..8ffae73dea6c 100644
> --- a/include/linux/sunrpc/xprtsock.h
> +++ b/include/linux/sunrpc/xprtsock.h
> @@ -56,6 +56,7 @@ struct sock_xprt {
> */
> unsigned long sock_state;
> struct delayed_work connect_worker;
> + int xprt_err;
Perhaps move this down just after srcport so we don't create an
unnecessary hole in the structure?
> struct work_struct error_worker;
> struct work_struct recv_worker;
> struct mutex recv_mutex;
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index e2176c167a57..7fe77eef7080 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -1250,12 +1250,12 @@ static void xs_error_report(struct sock *sk)
> goto out;
>
> transport = container_of(xprt, struct sock_xprt, xprt);
> - err = -sk->sk_err;
> - if (err == 0)
> + transport->xprt_err = -sk->sk_err;
Doesn't this need a smp write barrier to ensure it isn't reordered with
the set_bit() in xs_run_error_worker()?
> + if (transport->xprt_err == 0)
> goto out;
> dprintk("RPC: xs_error_report client %p, error=%d...\n",
> - xprt, -err);
> - trace_rpc_socket_error(xprt, sk->sk_socket, err);
> + xprt, -transport->xprt_err);
> + trace_rpc_socket_error(xprt, sk->sk_socket, transport-
> >xprt_err);
> xs_run_error_worker(transport, XPRT_SOCK_WAKE_ERROR);
> out:
> read_unlock_bh(&sk->sk_callback_lock);
> @@ -2470,7 +2470,6 @@ static void xs_wake_write(struct sock_xprt
> *transport)
> static void xs_wake_error(struct sock_xprt *transport)
> {
> int sockerr;
> - int sockerr_len = sizeof(sockerr);
>
> if (!test_bit(XPRT_SOCK_WAKE_ERROR, &transport->sock_state))
> return;
> @@ -2479,9 +2478,7 @@ static void xs_wake_error(struct sock_xprt
> *transport)
> goto out;
> if (!test_and_clear_bit(XPRT_SOCK_WAKE_ERROR, &transport-
> >sock_state))
> goto out;
> - if (kernel_getsockopt(transport->sock, SOL_SOCKET, SO_ERROR,
> - (char *)&sockerr, &sockerr_len) != 0)
> - goto out;
> + sockerr = xchg(&transport->xprt_err, 0);
> if (sockerr < 0)
> xprt_wake_pending_tasks(&transport->xprt, sockerr);
> out:
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] SUNRPC: fix race to sk_err after xs_error_report
2019-10-01 19:38 ` Trond Myklebust
@ 2019-10-02 10:41 ` Benjamin Coddington
0 siblings, 0 replies; 3+ messages in thread
From: Benjamin Coddington @ 2019-10-02 10:41 UTC (permalink / raw)
To: Trond Myklebust; +Cc: Anna.Schumaker, linux-nfs, jamespharvey20
On 1 Oct 2019, at 15:38, Trond Myklebust wrote:
> On Tue, 2019-10-01 at 14:30 -0400, Benjamin Coddington wrote:
>> ...
>> diff --git a/include/linux/sunrpc/xprtsock.h
>> b/include/linux/sunrpc/xprtsock.h
>> index 7638dbe7bc50..8ffae73dea6c 100644
>> --- a/include/linux/sunrpc/xprtsock.h
>> +++ b/include/linux/sunrpc/xprtsock.h
>> @@ -56,6 +56,7 @@ struct sock_xprt {
>> */
>> unsigned long sock_state;
>> struct delayed_work connect_worker;
>> + int xprt_err;
>
> Perhaps move this down just after srcport so we don't create an
> unnecessary hole in the structure?
Ok!
>> struct work_struct error_worker;
>> struct work_struct recv_worker;
>> struct mutex recv_mutex;
>> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
>> index e2176c167a57..7fe77eef7080 100644
>> --- a/net/sunrpc/xprtsock.c
>> +++ b/net/sunrpc/xprtsock.c
>> @@ -1250,12 +1250,12 @@ static void xs_error_report(struct sock *sk)
>> goto out;
>>
>> transport = container_of(xprt, struct sock_xprt, xprt);
>> - err = -sk->sk_err;
>> - if (err == 0)
>> + transport->xprt_err = -sk->sk_err;
>
> Doesn't this need a smp write barrier to ensure it isn't reordered with
> the set_bit() in xs_run_error_worker()?
Yes, it does need that or the error_worker may clear the bit without seeing
the error.
Ben
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-10-01 18:30 [PATCH] SUNRPC: fix race to sk_err after xs_error_report Benjamin Coddington
2019-10-01 19:38 ` Trond Myklebust
2019-10-02 10:41 ` Benjamin Coddington
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