Re: [PATCH net-next] rds: tcp: must use spin_lock_irq* and not spin_lock_bh with rds_tcp_conn_lock

[David Miller]

From: Sowmini Varadhan 
Date: Thu, 15 Mar 2018 03:54:26 -0700

> rds_tcp_connection allocation/free management has the potential to be
> called from __rds_conn_create after IRQs have been disabled, so
> spin_[un]lock_bh cannot be used with rds_tcp_conn_lock.
> 
> Bottom-halves that need to synchronize for critical sections protected
> by rds_tcp_conn_lock should instead use rds_destroy_pending() correctly.
> 
> Reported-by: syzbot+c68e51bb5e699d3f8...@syzkaller.appspotmail.com
> Fixes: ebeeb1ad9b8a ("rds: tcp: use rds_destroy_pending() to synchronize
>netns/module teardown and rds connection/workq management")
> Signed-off-by: Sowmini Varadhan 

Applied, thank you.

Re: [PATCH net-next] rds: tcp: must use spin_lock_irq* and not spin_lock_bh with rds_tcp_conn_lock

[Santosh Shilimkar]

On 3/15/2018 3:54 AM, Sowmini Varadhan wrote:

rds_tcp_connection allocation/free management has the potential to be
called from __rds_conn_create after IRQs have been disabled, so
spin_[un]lock_bh cannot be used with rds_tcp_conn_lock.

Bottom-halves that need to synchronize for critical sections protected
by rds_tcp_conn_lock should instead use rds_destroy_pending() correctly.

Reported-by: syzbot+c68e51bb5e699d3f8...@syzkaller.appspotmail.com
Fixes: ebeeb1ad9b8a ("rds: tcp: use rds_destroy_pending() to synchronize
netns/module teardown and rds connection/workq management")
Signed-off-by: Sowmini Varadhan 
---

Thanks Sowmini for the WARN_ON() discussion off-list.

Acked-by: Santosh Shilimkar 

[PATCH net-next] rds: tcp: must use spin_lock_irq* and not spin_lock_bh with rds_tcp_conn_lock

[Sowmini Varadhan]

rds_tcp_connection allocation/free management has the potential to be
called from __rds_conn_create after IRQs have been disabled, so
spin_[un]lock_bh cannot be used with rds_tcp_conn_lock.

Bottom-halves that need to synchronize for critical sections protected
by rds_tcp_conn_lock should instead use rds_destroy_pending() correctly.

Reported-by: syzbot+c68e51bb5e699d3f8...@syzkaller.appspotmail.com
Fixes: ebeeb1ad9b8a ("rds: tcp: use rds_destroy_pending() to synchronize
   netns/module teardown and rds connection/workq management")
Signed-off-by: Sowmini Varadhan 
---
 net/rds/tcp.c |   17 +
 1 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index eb04e7f..08ea9cd 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -272,13 +272,14 @@ static int rds_tcp_laddr_check(struct net *net, __be32 
addr)
 static void rds_tcp_conn_free(void *arg)
 {
struct rds_tcp_connection *tc = arg;
+   unsigned long flags;
 
rdsdebug("freeing tc %p\n", tc);
 
-   spin_lock_bh(_tcp_conn_lock);
+   spin_lock_irqsave(_tcp_conn_lock, flags);
if (!tc->t_tcp_node_detached)
list_del(>t_tcp_node);
-   spin_unlock_bh(_tcp_conn_lock);
+   spin_unlock_irqrestore(_tcp_conn_lock, flags);
 
kmem_cache_free(rds_tcp_conn_slab, tc);
 }
@@ -308,13 +309,13 @@ static int rds_tcp_conn_alloc(struct rds_connection 
*conn, gfp_t gfp)
rdsdebug("rds_conn_path [%d] tc %p\n", i,
 conn->c_path[i].cp_transport_data);
}
-   spin_lock_bh(_tcp_conn_lock);
+   spin_lock_irq(_tcp_conn_lock);
for (i = 0; i < RDS_MPATH_WORKERS; i++) {
tc = conn->c_path[i].cp_transport_data;
tc->t_tcp_node_detached = false;
list_add_tail(>t_tcp_node, _tcp_conn_list);
}
-   spin_unlock_bh(_tcp_conn_lock);
+   spin_unlock_irq(_tcp_conn_lock);
 fail:
if (ret) {
for (j = 0; j < i; j++)
@@ -527,7 +528,7 @@ static void rds_tcp_kill_sock(struct net *net)
 
rtn->rds_tcp_listen_sock = NULL;
rds_tcp_listen_stop(lsock, >rds_tcp_accept_w);
-   spin_lock_bh(_tcp_conn_lock);
+   spin_lock_irq(_tcp_conn_lock);
list_for_each_entry_safe(tc, _tc, _tcp_conn_list, t_tcp_node) {
struct net *c_net = read_pnet(>t_cpath->cp_conn->c_net);
 
@@ -540,7 +541,7 @@ static void rds_tcp_kill_sock(struct net *net)
tc->t_tcp_node_detached = true;
}
}
-   spin_unlock_bh(_tcp_conn_lock);
+   spin_unlock_irq(_tcp_conn_lock);
list_for_each_entry_safe(tc, _tc, _list, t_tcp_node)
rds_conn_destroy(tc->t_cpath->cp_conn);
 }
@@ -588,7 +589,7 @@ static void rds_tcp_sysctl_reset(struct net *net)
 {
struct rds_tcp_connection *tc, *_tc;
 
-   spin_lock_bh(_tcp_conn_lock);
+   spin_lock_irq(_tcp_conn_lock);
list_for_each_entry_safe(tc, _tc, _tcp_conn_list, t_tcp_node) {
struct net *c_net = read_pnet(>t_cpath->cp_conn->c_net);
 
@@ -598,7 +599,7 @@ static void rds_tcp_sysctl_reset(struct net *net)
/* reconnect with new parameters */
rds_conn_path_drop(tc->t_cpath, false);
}
-   spin_unlock_bh(_tcp_conn_lock);
+   spin_unlock_irq(_tcp_conn_lock);
 }
 
 static int rds_tcp_skbuf_handler(struct ctl_table *ctl, int write,
-- 
1.7.1