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net: sched: do not use tcf_proto 'tp' argument from call_rcu

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Using the tcf_proto pointer 'tp' from inside the classifiers callback
is not valid because it may have been cleaned up by another call_rcu
occuring on another CPU.

'tp' is currently being used by tcf_unbind_filter() in this patch we
move instances of tcf_unbind_filter outside of the call_rcu() context.
This is safe to do because any running schedulers will either read the
valid class field or it will be zeroed.

And all schedulers today when the class is 0 do a lookup using the
same call used by the tcf_exts_bind(). So even if we have a running
classifier hit the null class pointer it will do a lookup and get
to the same result. This is particularly fragile at the moment because
the only way to verify this is to audit the schedulers call sites.

Reported-by: Cong Wang <xiyou.wangconf@gmail.com>
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
John Fastabend 2014-10-05 21:28:52 -07:00 committed by David S. Miller
parent 13990f8156
commit 18cdb37ebf
4 changed files with 14 additions and 8 deletions
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5
net/sched/cls_basic.c
View File

@ -91,9 +91,7 @@ static int basic_init(struct tcf_proto *tp)
static void basic_delete_filter(struct rcu_head *head)
{
struct basic_filter *f = container_of(head, struct basic_filter, rcu);
struct tcf_proto *tp = f->tp;
tcf_unbind_filter(tp, &f->res);
tcf_exts_destroy(&f->exts);
tcf_em_tree_destroy(&f->ematches);
kfree(f);
@ -106,6 +104,7 @@ static void basic_destroy(struct tcf_proto *tp)
list_for_each_entry_safe(f, n, &head->flist, link) {
list_del_rcu(&f->link);
tcf_unbind_filter(tp, &f->res);
call_rcu(&f->rcu, basic_delete_filter);
}
RCU_INIT_POINTER(tp->root, NULL);
@ -120,6 +119,7 @@ static int basic_delete(struct tcf_proto *tp, unsigned long arg)
list_for_each_entry(t, &head->flist, link)
if (t == f) {
list_del_rcu(&t->link);
tcf_unbind_filter(tp, &t->res);
call_rcu(&t->rcu, basic_delete_filter);
return 0;
}
@ -222,6 +222,7 @@ static int basic_change(struct net *net, struct sk_buff *in_skb,
if (fold) {
list_replace_rcu(&fold->link, &fnew->link);
tcf_unbind_filter(tp, &fold->res);
call_rcu(&fold->rcu, basic_delete_filter);
} else {
list_add_rcu(&fnew->link, &head->flist);

4
net/sched/cls_bpf.c
View File

@ -92,7 +92,6 @@ static int cls_bpf_init(struct tcf_proto *tp)
static void cls_bpf_delete_prog(struct tcf_proto *tp, struct cls_bpf_prog *prog)
{
tcf_unbind_filter(tp, &prog->res);
tcf_exts_destroy(&prog->exts);
bpf_prog_destroy(prog->filter);
@ -116,6 +115,7 @@ static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)
list_for_each_entry(prog, &head->plist, link) {
if (prog == todel) {
list_del_rcu(&prog->link);
tcf_unbind_filter(tp, &prog->res);
call_rcu(&prog->rcu, __cls_bpf_delete_prog);
return 0;
}
@ -131,6 +131,7 @@ static void cls_bpf_destroy(struct tcf_proto *tp)
list_for_each_entry_safe(prog, tmp, &head->plist, link) {
list_del_rcu(&prog->link);
tcf_unbind_filter(tp, &prog->res);
call_rcu(&prog->rcu, __cls_bpf_delete_prog);
}
@ -282,6 +283,7 @@ static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
if (oldprog) {
list_replace_rcu(&prog->link, &oldprog->link);
tcf_unbind_filter(tp, &oldprog->res);
call_rcu(&oldprog->rcu, __cls_bpf_delete_prog);
} else {
list_add_rcu(&prog->link, &head->plist);

5
net/sched/cls_fw.c
View File

@ -123,9 +123,7 @@ static int fw_init(struct tcf_proto *tp)
static void fw_delete_filter(struct rcu_head *head)
{
struct fw_filter *f = container_of(head, struct fw_filter, rcu);
struct tcf_proto *tp = f->tp;
tcf_unbind_filter(tp, &f->res);
tcf_exts_destroy(&f->exts);
kfree(f);
}
@ -143,6 +141,7 @@ static void fw_destroy(struct tcf_proto *tp)
while ((f = rtnl_dereference(head->ht[h])) != NULL) {
RCU_INIT_POINTER(head->ht[h],
rtnl_dereference(f->next));
tcf_unbind_filter(tp, &f->res);
call_rcu(&f->rcu, fw_delete_filter);
}
}
@ -166,6 +165,7 @@ static int fw_delete(struct tcf_proto *tp, unsigned long arg)
fp = &pfp->next, pfp = rtnl_dereference(*fp)) {
if (pfp == f) {
RCU_INIT_POINTER(*fp, rtnl_dereference(f->next));
tcf_unbind_filter(tp, &f->res);
call_rcu(&f->rcu, fw_delete_filter);
return 0;
}
@ -280,6 +280,7 @@ static int fw_change(struct net *net, struct sk_buff *in_skb,
RCU_INIT_POINTER(fnew->next, rtnl_dereference(pfp->next));
rcu_assign_pointer(*fp, fnew);
tcf_unbind_filter(tp, &f->res);
call_rcu(&f->rcu, fw_delete_filter);
*arg = (unsigned long)fnew;

8
net/sched/cls_route.c
View File

@ -269,9 +269,7 @@ static void
route4_delete_filter(struct rcu_head *head)
{
struct route4_filter *f = container_of(head, struct route4_filter, rcu);
struct tcf_proto *tp = f->tp;
tcf_unbind_filter(tp, &f->res);
tcf_exts_destroy(&f->exts);
kfree(f);
}
@ -297,6 +295,7 @@ static void route4_destroy(struct tcf_proto *tp)
next = rtnl_dereference(f->next);
RCU_INIT_POINTER(b->ht[h2], next);
tcf_unbind_filter(tp, &f->res);
call_rcu(&f->rcu, route4_delete_filter);
}
}
@ -338,6 +337,7 @@ static int route4_delete(struct tcf_proto *tp, unsigned long arg)
route4_reset_fastmap(head);
/* Delete it */
tcf_unbind_filter(tp, &f->res);
call_rcu(&f->rcu, route4_delete_filter);
/* Strip RTNL protected tree */
@ -545,8 +545,10 @@ static int route4_change(struct net *net, struct sk_buff *in_skb,
route4_reset_fastmap(head);
*arg = (unsigned long)f;
if (fold)
if (fold) {
tcf_unbind_filter(tp, &fold->res);
call_rcu(&fold->rcu, route4_delete_filter);
}
return 0;
errout: