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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
Download Patch File Download Diff File Expand all files Collapse all files

20
net/ipv6/ip6_fib.c
View File

@@ -148,11 +148,23 @@ static struct fib6_node *node_alloc(void)
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);
}
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)
{
int cpu;
@@ -601,9 +613,9 @@ insert_above:
if (!in || !ln) {
if (in)
node_free(in);
node_free_immediate(in);
if (ln)
node_free(ln);
node_free_immediate(ln);
return ERR_PTR(-ENOMEM);
}
@@ -1038,7 +1050,7 @@ int fib6_add(struct fib6_node *root, struct rt6_info *rt,
root, and then (in failure) stale node
in main tree.
*/
node_free(sfn);
node_free_immediate(sfn);
err = PTR_ERR(sn);
goto failure;
}