From: Xin Long lucien.xin@gmail.com
[ Upstream commit 3106ecb43a05dc3e009779764b9da245a5d082de ]
With disabling bh in the whole sctp_get_port_local(), when snum == 0 and too many ports have been used, the do-while loop will take the cpu for a long time and cause cpu stuck:
[ ] watchdog: BUG: soft lockup - CPU#11 stuck for 22s! [ ] RIP: 0010:native_queued_spin_lock_slowpath+0x4de/0x940 [ ] Call Trace: [ ] _raw_spin_lock+0xc1/0xd0 [ ] sctp_get_port_local+0x527/0x650 [sctp] [ ] sctp_do_bind+0x208/0x5e0 [sctp] [ ] sctp_autobind+0x165/0x1e0 [sctp] [ ] sctp_connect_new_asoc+0x355/0x480 [sctp] [ ] __sctp_connect+0x360/0xb10 [sctp]
There's no need to disable bh in the whole function of sctp_get_port_local. So fix this cpu stuck by removing local_bh_disable() called at the beginning, and using spin_lock_bh() instead.
The same thing was actually done for inet_csk_get_port() in Commit ea8add2b1903 ("tcp/dccp: better use of ephemeral ports in bind()").
Thanks to Marcelo for pointing the buggy code out.
v1->v2: - use cond_resched() to yield cpu to other tasks if needed, as Eric noticed.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Ying Xu yinxu@redhat.com Signed-off-by: Xin Long lucien.xin@gmail.com Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sctp/socket.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-)
--- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -8297,8 +8297,6 @@ static int sctp_get_port_local(struct so
pr_debug("%s: begins, snum:%d\n", __func__, snum);
- local_bh_disable(); - if (snum == 0) { /* Search for an available port. */ int low, high, remaining, index; @@ -8316,20 +8314,21 @@ static int sctp_get_port_local(struct so continue; index = sctp_phashfn(net, rover); head = &sctp_port_hashtable[index]; - spin_lock(&head->lock); + spin_lock_bh(&head->lock); sctp_for_each_hentry(pp, &head->chain) if ((pp->port == rover) && net_eq(net, pp->net)) goto next; break; next: - spin_unlock(&head->lock); + spin_unlock_bh(&head->lock); + cond_resched(); } while (--remaining > 0);
/* Exhausted local port range during search? */ ret = 1; if (remaining <= 0) - goto fail; + return ret;
/* OK, here is the one we will use. HEAD (the port * hash table list entry) is non-NULL and we hold it's @@ -8344,7 +8343,7 @@ static int sctp_get_port_local(struct so * port iterator, pp being NULL. */ head = &sctp_port_hashtable[sctp_phashfn(net, snum)]; - spin_lock(&head->lock); + spin_lock_bh(&head->lock); sctp_for_each_hentry(pp, &head->chain) { if ((pp->port == snum) && net_eq(pp->net, net)) goto pp_found; @@ -8444,10 +8443,7 @@ success: ret = 0;
fail_unlock: - spin_unlock(&head->lock); - -fail: - local_bh_enable(); + spin_unlock_bh(&head->lock); return ret; }