Commit dfcb9f4f99f1 ("sctp: deny peeloff operation on asocs with threads
sleeping on it") fixed the race between peeloff and wait sndbuf by
checking waitqueue_active(&asoc->wait) in sctp_do_peeloff().
But it actually doesn't work as even if waitqueue_active returns false
the waiting sndbuf thread may still not yet hold sk lock.
This patch is to fix this by adding wait_buf flag in asoc, and setting it
before going the waiting loop, clearing it until the waiting loop breaks,
and checking it in sctp_do_peeloff instead.
Fixes: dfcb9f4f99f1 ("sctp: deny peeloff operation on asocs with threads sleeping on it")
Suggested-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
---
include/net/sctp/structs.h | 1 +
net/sctp/socket.c | 4 +++-
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 0477945..446350e 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1883,6 +1883,7 @@ struct sctp_association {
__u8 need_ecne:1, /* Need to send an ECNE Chunk? */
temp:1, /* Is it a temporary association? */
+ wait_buf:1,
force_delay:1,
prsctp_enable:1,
reconf_enable:1;
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 6f45d17..1b2c78c 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4946,7 +4946,7 @@ int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id, struct socket **sockp)
/* If there is a thread waiting on more sndbuf space for
* sending on this asoc, it cannot be peeled.
*/
- if (waitqueue_active(&asoc->wait))
+ if (asoc->wait_buf)
return -EBUSY;
/* An association cannot be branched off from an already peeled-off
@@ -7835,6 +7835,7 @@ static int sctp_wait_for_sndbuf(struct sctp_association *asoc, long *timeo_p,
/* Increment the association's refcnt. */
sctp_association_hold(asoc);
+ asoc->wait_buf = 1;
/* Wait on the association specific sndbuf space. */
for (;;) {
prepare_to_wait_exclusive(&asoc->wait, &wait,
@@ -7860,6 +7861,7 @@ static int sctp_wait_for_sndbuf(struct sctp_association *asoc, long *timeo_p,
}
out:
+ asoc->wait_buf = 0;
finish_wait(&asoc->wait, &wait);
/* Release the association's refcnt. */
--
2.1.0
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