[PATCHv2 net] sctp: not disable bh in the whole sctp_get_port_local()
From: Xin Long <lucien.xin@gmail.com>
Date: 2020-08-21 06:59:50
Also in:
linux-sctp
Subsystem:
networking [general], sctp protocol, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Marcelo Ricardo Leitner, Xin Long, Linus Torvalds
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 <redacted>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
net/sctp/socket.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index ec1fba1..836615f 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c@@ -8060,8 +8060,6 @@ static int sctp_get_port_local(struct sock *sk, union sctp_addr *addr) 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;
@@ -8079,20 +8077,21 @@ static int sctp_get_port_local(struct sock *sk, union sctp_addr *addr) 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
@@ -8107,7 +8106,7 @@ static int sctp_get_port_local(struct sock *sk, union sctp_addr *addr) * 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;
@@ -8207,10 +8206,7 @@ static int sctp_get_port_local(struct sock *sk, union sctp_addr *addr) ret = 0; fail_unlock: - spin_unlock(&head->lock); - -fail: - local_bh_enable(); + spin_unlock_bh(&head->lock); return ret; }
--
2.1.0