[PATCH 4.11 012/115] tipc: make macro tipc_wait_for_cond() smp safe

Greg Kroah-Hartman
2017-06-05T16:56:53Z

From: Jon Paul Maloy <jon.maloy@ericsson.com>

[ Upstream commit 844cf763fba654436d3a4279b6a672c196cf1901 ]

The macro tipc_wait_for_cond() is embedding the macro sk_wait_event()
to fulfil its task. The latter, in turn, is evaluating the stated
condition outside the socket lock context. This is problematic if
the condition is accessing non-trivial data structures which may be
altered by incoming interrupts, as is the case with the cong_links()
linked list, used by socket to keep track of the current set of
congested links. We sometimes see crashes when this list is accessed
by a condition function at the same time as a SOCK_WAKEUP interrupt
is removing an element from the list.

We fix this by expanding selected parts of sk_wait_event() into the
outer macro, while ensuring that all evaluations of a given condition
are performed under socket lock protection.

Fixes: commit 365ad353c256 ("tipc: reduce risk of user starvation during link congestion")
Reviewed-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/tipc/socket.c | 38 +++++++++++++++++++-------------------
1 file changed, 19 insertions(+), 19 deletions(-)

--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -361,25 +361,25 @@ static int tipc_sk_sock_err(struct socke
return 0;
}

-#define tipc_wait_for_cond(sock_, timeout_, condition_) \
-({ \
- int rc_ = 0; \
- int done_ = 0; \
- \
- while (!(condition_) && !done_) { \
- struct sock *sk_ = sock->sk; \
- DEFINE_WAIT_FUNC(wait_, woken_wake_function); \
- \
- rc_ = tipc_sk_sock_err(sock_, timeout_); \
- if (rc_) \
- break; \
- prepare_to_wait(sk_sleep(sk_), &wait_, \
- TASK_INTERRUPTIBLE); \
- done_ = sk_wait_event(sk_, timeout_, \
- (condition_), &wait_); \
- remove_wait_queue(sk_sleep(sk_), &wait_); \
- } \
- rc_; \
+#define tipc_wait_for_cond(sock_, timeo_, condition_) \
+({ \
+ struct sock *sk_; \
+ int rc_; \
+ \
+ while ((rc_ = !(condition_))) { \
+ DEFINE_WAIT_FUNC(wait_, woken_wake_function); \
+ sk_ = (sock_)->sk; \
+ rc_ = tipc_sk_sock_err((sock_), timeo_); \
+ if (rc_) \
+ break; \
+ prepare_to_wait(sk_sleep(sk_), &wait_, TASK_INTERRUPTIBLE); \
+ release_sock(sk_); \
+ *(timeo_) = wait_woken(&wait_, TASK_INTERRUPTIBLE, *(timeo_)); \
+ sched_annotate_sleep(); \
+ lock_sock(sk_); \
+ remove_wait_queue(sk_sleep(sk_), &wait_); \
+ } \
+ rc_; \
})

/**