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ipv6: add rcu grace period before freeing fib6_node

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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: Wei Wang <weiwan@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wei Wang
2017-08-21 09:47:10 -07:00
committed by David S. Miller
parent 0c8d2d95b8
commit c5cff8561d
3 changed files with 56 additions and 8 deletions
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30
include/net/ip6_fib.h
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@@ -70,6 +70,7 @@ struct fib6_node {
__u16 fn_flags;
int fn_sernum;
struct rt6_info *rr_ptr;
struct rcu_head rcu;
};
#ifndef CONFIG_IPV6_SUBTREES
@@ -167,13 +168,40 @@ static inline void rt6_update_expires(struct rt6_info *rt0, int timeout)
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)
{
u32 cookie = 0;
if (rt->rt6i_flags & RTF_PCPU ||
(unlikely(!list_empty(&rt->rt6i_uncached)) && 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)