On 01.12.2017 15:18, Ying Xue wrote:
On 11/30/2017 08:32 PM, Tommi Rantala wrote:
In my opinion, the real root cause of the issue is because we too early
set a not-yet-initialized bearer instance to ub->bearer through
rcu_assign_pointer(ub->bearer, b) in tipc_udp_enable(). Instead if we
assign the bearer pointer at the end of tipc_udp_enable() where the
bearer has been completed the initialization, the issue would be avoided.
Hi, sorry, I fail to see how that helps.
bearer->tolerance is only initialized in tipc_enable_bearer() after
calling m->enable_media() ie. tipc_udp_enable().
So even if we do "rcu_assign_pointer(ub->bearer, b)" later in
tipc_udp_enable(), bearer->tolerance will still be uninitialized, and
the crash can happen.
Sorry, I missed the point that b->tolerance is not uninitialized when we
assign bearer pointer to ub->bearer later.
But in my view the issue happened is because we enable media too early.
So it's better to change the code as belows:
Thanks, looks good to me!
Tested in 4.4 (which does not have b->up), and this fixes the oops also
there.
-Tommi
diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index 47ec121..ec6f02a 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -320,19 +320,18 @@ static int tipc_enable_bearer(struct net *net,
const char *name,
strcpy(b->name, name);
b->media = m;
- res = m->enable_media(net, b, attr);
- if (res) {
- pr_warn("Bearer <%s> rejected, enable failure (%d)\n",
- name, -res);
- return -EINVAL;
- }
-
b->identity = bearer_id;
b->tolerance = m->tolerance;
b->window = m->window;
b->domain = disc_domain;
b->net_plane = bearer_id + 'A';
b->priority = priority;
+ res = m->enable_media(net, b, attr);
+ if (res) {
+ pr_warn("Bearer <%s> rejected, enable failure (%d)\n",
+ name, -res);
+ return -EINVAL;
+ }
test_and_set_bit_lock(0, &b->up);
