net: Fix bridgeing sysfs handling of rtnl_lock

Holding rtnl_lock when we are unregistering the sysfs files can
deadlock if we unconditionally take rtnl_lock in a sysfs file.  So fix
it with the now familiar patter of: rtnl_trylock and syscall_restart()

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 4 insertions, 2 deletions

diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
index 603d89248e71..ee4820aa1843 100644
--- a/net/bridge/br_sysfs_br.c
+++ b/net/bridge/br_sysfs_br.c
@@ -172,7 +172,8 @@ static ssize_t store_stp_state(struct device *d,
         if (endp == buf)
                 return -EINVAL;
 
-        rtnl_lock();
+        if (!rtnl_trylock())
+                return restart_syscall();
         br_stp_set_enabled(br, val);
         rtnl_unlock();
 
diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
index 02b2d50cce4d..4a3cdf8f3813 100644
--- a/net/bridge/br_sysfs_if.c
+++ b/net/bridge/br_sysfs_if.c
@@ -189,7 +189,8 @@ static ssize_t brport_store(struct kobject * kobj,
 
         val = simple_strtoul(buf, &endp, 0);
         if (endp != buf) {
-                rtnl_lock();
+                if (!rtnl_trylock())
+                        return restart_syscall();
                 if (p->dev && p->br && brport_attr->store) {
                         spin_lock_bh(&p->br->lock);
                         ret = brport_attr->store(p, val);