On Tue, 2017-06-06 at 18:00 -0600, David Ahern wrote:
> On 6/6/17 3:06 PM, Ben Greear wrote:
> > This bug has been around forever, and we recently got an intern and
> > stuck him with
> > trying to reproduce it on the latest kernel. It is still here. I'm not
> > super excited
> > about trying to fix this, but we can easily test patches if someone has a
> > patch to try.
>
> Can you try this (whitespace damaged on paste, but it is moving the lock
> ahead of the fn_sernum check):
>
> diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
> index deea901746c8..7a44c49055c0 100644
> --- a/net/ipv6/ip6_fib.c
> +++ b/net/ipv6/ip6_fib.c
> @@ -378,6 +378,7 @@ static int fib6_dump_table(struct fib6_table *table,
> struct sk_buff *skb,
> cb->args[5] = w->root->fn_sernum;
> }
> } else {
> + read_lock_bh(&table->tb6_lock);
> if (cb->args[5] != w->root->fn_sernum) {
> /* Begin at the root if the tree changed */
> cb->args[5] = w->root->fn_sernum;
> @@ -387,7 +388,6 @@ static int fib6_dump_table(struct fib6_table *table,
> struct sk_buff *skb,
> } else
> w->skip = 0;
>
> - read_lock_bh(&table->tb6_lock);
> res = fib6_walk_continue(w);
> read_unlock_bh(&table->tb6_lock);
> if (res <= 0) {
Good catch, but it looks like similar fix is needed a few lines before.
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index
deea901746c8570c5e801e40592c91e3b62812e0..b214443dc8346cef3690df7f27cc48a864028865
100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -372,12 +372,13 @@ static int fib6_dump_table(struct fib6_table *table,
struct sk_buff *skb,
read_lock_bh(&table->tb6_lock);
res = fib6_walk(net, w);
- read_unlock_bh(&table->tb6_lock);
if (res > 0) {
cb->args[4] = 1;
cb->args[5] = w->root->fn_sernum;
}
+ read_unlock_bh(&table->tb6_lock);
} else {
+ read_lock_bh(&table->tb6_lock);
if (cb->args[5] != w->root->fn_sernum) {
/* Begin at the root if the tree changed */
cb->args[5] = w->root->fn_sernum;
@@ -387,7 +388,6 @@ static int fib6_dump_table(struct fib6_table *table, struct
sk_buff *skb,
} else
w->skip = 0;
- read_lock_bh(&table->tb6_lock);
res = fib6_walk_continue(w);
read_unlock_bh(&table->tb6_lock);
if (res <= 0) {
