Commit c5cff856 authored by Wei Wang's avatar Wei Wang Committed by David S. Miller

ipv6: add rcu grace period before freeing fib6_node

We currently keep rt->rt6i_node pointing to the fib6_node for the route.
And some functions make use of this pointer to dereference the fib6_node
from rt structure, e.g. rt6_check(). However, as there is neither
refcount nor rcu taken when dereferencing rt->rt6i_node, it could
potentially cause crashes as rt->rt6i_node could be set to NULL by other
CPUs when doing a route deletion.
This patch introduces an rcu grace period before freeing fib6_node and
makes sure the functions that dereference it takes rcu_read_lock().

Note: there is no "Fixes" tag because this bug was there in a very
early stage.
Signed-off-by: default avatarWei Wang <weiwan@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0c8d2d95
...@@ -70,6 +70,7 @@ struct fib6_node { ...@@ -70,6 +70,7 @@ struct fib6_node {
__u16 fn_flags; __u16 fn_flags;
int fn_sernum; int fn_sernum;
struct rt6_info *rr_ptr; struct rt6_info *rr_ptr;
struct rcu_head rcu;
}; };
#ifndef CONFIG_IPV6_SUBTREES #ifndef CONFIG_IPV6_SUBTREES
...@@ -167,13 +168,40 @@ static inline void rt6_update_expires(struct rt6_info *rt0, int timeout) ...@@ -167,13 +168,40 @@ static inline void rt6_update_expires(struct rt6_info *rt0, int timeout)
rt0->rt6i_flags |= RTF_EXPIRES; rt0->rt6i_flags |= RTF_EXPIRES;
} }
/* Function to safely get fn->sernum for passed in rt
* and store result in passed in cookie.
* Return true if we can get cookie safely
* Return false if not
*/
static inline bool rt6_get_cookie_safe(const struct rt6_info *rt,
u32 *cookie)
{
struct fib6_node *fn;
bool status = false;
rcu_read_lock();
fn = rcu_dereference(rt->rt6i_node);
if (fn) {
*cookie = fn->fn_sernum;
status = true;
}
rcu_read_unlock();
return status;
}
static inline u32 rt6_get_cookie(const struct rt6_info *rt) static inline u32 rt6_get_cookie(const struct rt6_info *rt)
{ {
u32 cookie = 0;
if (rt->rt6i_flags & RTF_PCPU || if (rt->rt6i_flags & RTF_PCPU ||
(unlikely(!list_empty(&rt->rt6i_uncached)) && rt->dst.from)) (unlikely(!list_empty(&rt->rt6i_uncached)) && rt->dst.from))
rt = (struct rt6_info *)(rt->dst.from); rt = (struct rt6_info *)(rt->dst.from);
return rt->rt6i_node ? rt->rt6i_node->fn_sernum : 0; rt6_get_cookie_safe(rt, &cookie);
return cookie;
} }
static inline void ip6_rt_put(struct rt6_info *rt) static inline void ip6_rt_put(struct rt6_info *rt)
......
...@@ -148,11 +148,23 @@ static struct fib6_node *node_alloc(void) ...@@ -148,11 +148,23 @@ static struct fib6_node *node_alloc(void)
return fn; return fn;
} }
static void node_free(struct fib6_node *fn) static void node_free_immediate(struct fib6_node *fn)
{
kmem_cache_free(fib6_node_kmem, fn);
}
static void node_free_rcu(struct rcu_head *head)
{ {
struct fib6_node *fn = container_of(head, struct fib6_node, rcu);
kmem_cache_free(fib6_node_kmem, fn); kmem_cache_free(fib6_node_kmem, fn);
} }
static void node_free(struct fib6_node *fn)
{
call_rcu(&fn->rcu, node_free_rcu);
}
static void rt6_free_pcpu(struct rt6_info *non_pcpu_rt) static void rt6_free_pcpu(struct rt6_info *non_pcpu_rt)
{ {
int cpu; int cpu;
...@@ -601,9 +613,9 @@ static struct fib6_node *fib6_add_1(struct fib6_node *root, ...@@ -601,9 +613,9 @@ static struct fib6_node *fib6_add_1(struct fib6_node *root,
if (!in || !ln) { if (!in || !ln) {
if (in) if (in)
node_free(in); node_free_immediate(in);
if (ln) if (ln)
node_free(ln); node_free_immediate(ln);
return ERR_PTR(-ENOMEM); return ERR_PTR(-ENOMEM);
} }
...@@ -1038,7 +1050,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt, ...@@ -1038,7 +1050,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
root, and then (in failure) stale node root, and then (in failure) stale node
in main tree. in main tree.
*/ */
node_free(sfn); node_free_immediate(sfn);
err = PTR_ERR(sn); err = PTR_ERR(sn);
goto failure; goto failure;
} }
......
...@@ -1289,7 +1289,9 @@ static void rt6_dst_from_metrics_check(struct rt6_info *rt) ...@@ -1289,7 +1289,9 @@ static void rt6_dst_from_metrics_check(struct rt6_info *rt)
static struct dst_entry *rt6_check(struct rt6_info *rt, u32 cookie) static struct dst_entry *rt6_check(struct rt6_info *rt, u32 cookie)
{ {
if (!rt->rt6i_node || (rt->rt6i_node->fn_sernum != cookie)) u32 rt_cookie;
if (!rt6_get_cookie_safe(rt, &rt_cookie) || rt_cookie != cookie)
return NULL; return NULL;
if (rt6_check_expired(rt)) if (rt6_check_expired(rt))
...@@ -1357,8 +1359,14 @@ static void ip6_link_failure(struct sk_buff *skb) ...@@ -1357,8 +1359,14 @@ static void ip6_link_failure(struct sk_buff *skb)
if (rt->rt6i_flags & RTF_CACHE) { if (rt->rt6i_flags & RTF_CACHE) {
if (dst_hold_safe(&rt->dst)) if (dst_hold_safe(&rt->dst))
ip6_del_rt(rt); ip6_del_rt(rt);
} else if (rt->rt6i_node && (rt->rt6i_flags & RTF_DEFAULT)) { } else {
rt->rt6i_node->fn_sernum = -1; struct fib6_node *fn;
rcu_read_lock();
fn = rcu_dereference(rt->rt6i_node);
if (fn && (rt->rt6i_flags & RTF_DEFAULT))
fn->fn_sernum = -1;
rcu_read_unlock();
} }
} }
} }
......
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