[PATCH 4.14 32/52] cls_bpf: dont decrement nets refcount when offload fails

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jakub Kicinski <jakub.kicinski@xxxxxxxxxxxxx>


[ Upstream commit 25415cec502a1232b19fffc85465882b19a90415 ]

When cls_bpf offload was added it seemed like a good idea to
call cls_bpf_delete_prog() instead of extending the error
handling path, since the software state is fully initialized
at that point.  This handling of errors without jumping to
the end of the function is error prone, as proven by later
commit missing that extra call to __cls_bpf_delete_prog().

__cls_bpf_delete_prog() is now expected to be invoked with
a reference on exts->net or the field zeroed out.  The call
on the offload's error patch does not fullfil this requirement,
leading to each error stealing a reference on net namespace.

Create a function undoing what cls_bpf_set_parms() did and
use it from __cls_bpf_delete_prog() and the error path.

Fixes: aae2c35ec892 ("cls_bpf: use tcf_exts_get_net() before call_rcu()")
Signed-off-by: Jakub Kicinski <jakub.kicinski@xxxxxxxxxxxxx>
Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxxx>
Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/sched/cls_bpf.c |   21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

--- a/net/sched/cls_bpf.c
+++ b/net/sched/cls_bpf.c
@@ -246,11 +246,8 @@ static int cls_bpf_init(struct tcf_proto
 	return 0;
 }
 
-static void __cls_bpf_delete_prog(struct cls_bpf_prog *prog)
+static void cls_bpf_free_parms(struct cls_bpf_prog *prog)
 {
-	tcf_exts_destroy(&prog->exts);
-	tcf_exts_put_net(&prog->exts);
-
 	if (cls_bpf_is_ebpf(prog))
 		bpf_prog_put(prog->filter);
 	else
@@ -258,6 +255,14 @@ static void __cls_bpf_delete_prog(struct
 
 	kfree(prog->bpf_name);
 	kfree(prog->bpf_ops);
+}
+
+static void __cls_bpf_delete_prog(struct cls_bpf_prog *prog)
+{
+	tcf_exts_destroy(&prog->exts);
+	tcf_exts_put_net(&prog->exts);
+
+	cls_bpf_free_parms(prog);
 	kfree(prog);
 }
 
@@ -509,10 +514,8 @@ static int cls_bpf_change(struct net *ne
 		goto errout;
 
 	ret = cls_bpf_offload(tp, prog, oldprog);
-	if (ret) {
-		__cls_bpf_delete_prog(prog);
-		return ret;
-	}
+	if (ret)
+		goto errout_parms;
 
 	if (!tc_in_hw(prog->gen_flags))
 		prog->gen_flags |= TCA_CLS_FLAGS_NOT_IN_HW;
@@ -529,6 +532,8 @@ static int cls_bpf_change(struct net *ne
 	*arg = prog;
 	return 0;
 
+errout_parms:
+	cls_bpf_free_parms(prog);
 errout:
 	tcf_exts_destroy(&prog->exts);
 	kfree(prog);