[PATCH bpf-next 0/2] test_bpf: Add an skb_segment test for a linear head_frag=0 skb whose gso_size was mangled

[PATCH bpf-next 0/2] test_bpf: Add an skb_segment test for a linear head_frag=0 skb whose gso_size was mangled

[Shmulik Ladkani]

Add a reproducer test that mimics the input skbs that lead to the BUG_ON
in skb_segment() which was fixed by commit 3dcbdb134f32 ("net: gso: Fix skb_segment splat when splitting gso_size mangled skb having linear-headed frag_list").

Shmulik Ladkani (2):
  test_bpf: Refactor test_skb_segment() to allow testing skb_segment()
    on numerous different skbs
  test_bpf: Introduce 'gso_linear_no_head_frag' skb_segment test

 lib/test_bpf.c | 112 +++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 103 insertions(+), 9 deletions(-)

-- 
2.17.1

[PATCH bpf-next 1/2] test_bpf: Refactor test_skb_segment() to allow testing skb_segment() on numerous different skbs

[Shmulik Ladkani]

Currently, test_skb_segment() builds a single test skb and runs
skb_segment() on it.

Extend test_skb_segment() so it processes an array of numerous
skb/feature pairs to test.

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
---
 lib/test_bpf.c | 51 ++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 10 deletions(-)

diff --git a/lib/test_bpf.c b/lib/test_bpf.c
index 5ef3eccee27c..c952df82b515 100644
--- a/lib/test_bpf.c
+++ b/lib/test_bpf.c
@@ -6859,34 +6859,65 @@ static __init struct sk_buff *build_test_skb(void)
 	return NULL;
 }
 
-static __init int test_skb_segment(void)
-{
+struct skb_segment_test {
+	const char *descr;
+	struct sk_buff *(*build_skb)(void);
 	netdev_features_t features;
+};
+
+static struct skb_segment_test skb_segment_tests[] __initconst = {
+	{
+		.descr = "gso_with_rx_frags",
+		.build_skb = build_test_skb,
+		.features = NETIF_F_SG | NETIF_F_GSO_PARTIAL | NETIF_F_IP_CSUM |
+			    NETIF_F_IPV6_CSUM | NETIF_F_RXCSUM
+	}
+};
+
+static __init int test_skb_segment_single(const struct skb_segment_test *test)
+{
 	struct sk_buff *skb, *segs;
 	int ret = -1;
 
-	features = NETIF_F_SG | NETIF_F_GSO_PARTIAL | NETIF_F_IP_CSUM |
-		   NETIF_F_IPV6_CSUM;
-	features |= NETIF_F_RXCSUM;
-	skb = build_test_skb();
+	skb = test->build_skb();
 	if (!skb) {
 		pr_info("%s: failed to build_test_skb", __func__);
 		goto done;
 	}
 
-	segs = skb_segment(skb, features);
+	segs = skb_segment(skb, test->features);
 	if (!IS_ERR(segs)) {
 		kfree_skb_list(segs);
 		ret = 0;
-		pr_info("%s: success in skb_segment!", __func__);
-	} else {
-		pr_info("%s: failed in skb_segment!", __func__);
 	}
 	kfree_skb(skb);
 done:
 	return ret;
 }
 
+static __init int test_skb_segment(void)
+{
+	int i, err_cnt = 0, pass_cnt = 0;
+
+	for (i = 0; i < ARRAY_SIZE(skb_segment_tests); i++) {
+		const struct skb_segment_test *test = &skb_segment_tests[i];
+
+		pr_info("#%d %s ", i, test->descr);
+
+		if (test_skb_segment_single(test)) {
+			pr_cont("FAIL\n");
+			err_cnt++;
+		} else {
+			pr_cont("PASS\n");
+			pass_cnt++;
+		}
+	}
+
+	pr_info("%s: Summary: %d PASSED, %d FAILED\n", __func__,
+		pass_cnt, err_cnt);
+	return err_cnt ? -EINVAL : 0;
+}
+
 static __init int test_bpf(void)
 {
 	int i, err_cnt = 0, pass_cnt = 0;
-- 
2.17.1

[PATCH bpf-next 2/2] test_bpf: Introduce 'gso_linear_no_head_frag' skb_segment test

[Shmulik Ladkani]

Following reports of skb_segment() hitting a BUG_ON when working on
GROed skbs which have their gso_size mangled (e.g. after a
bpf_skb_change_proto call), add a reproducer test that mimics the
input skbs that lead to the mentioned BUG_ON as in [1] and validates the
fix submitted in [2].

[1] https://lists.openwall.net/netdev/2019/08/26/110
[2] commit 3dcbdb134f32 ("net: gso: Fix skb_segment splat when splitting gso_size mangled skb having linear-headed frag_list")

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
---
 lib/test_bpf.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/lib/test_bpf.c b/lib/test_bpf.c
index c952df82b515..cecb230833be 100644
--- a/lib/test_bpf.c
+++ b/lib/test_bpf.c
@@ -6859,6 +6859,60 @@ static __init struct sk_buff *build_test_skb(void)
 	return NULL;
 }
 
+static __init struct sk_buff *build_test_skb_linear_no_head_frag(void)
+{
+	unsigned int alloc_size = 2000;
+	unsigned int headroom = 102, doffset = 72, data_size = 1308;
+	struct sk_buff *skb[2];
+	int i;
+
+	/* skbs linked in a frag_list, both with linear data, with head_frag=0
+	 * (data allocated by kmalloc), both have tcp data of 1308 bytes
+	 * (total payload is 2616 bytes).
+	 * Data offset is 72 bytes (40 ipv6 hdr, 32 tcp hdr). Some headroom.
+	 */
+	for (i = 0; i < 2; i++) {
+		skb[i] = alloc_skb(alloc_size, GFP_KERNEL);
+		if (!skb[i]) {
+			if (i == 0)
+				goto err_skb0;
+			else
+				goto err_skb1;
+		}
+
+		skb[i]->protocol = htons(ETH_P_IPV6);
+		skb_reserve(skb[i], headroom);
+		skb_put(skb[i], doffset + data_size);
+		skb_reset_network_header(skb[i]);
+		if (i == 0)
+			skb_reset_mac_header(skb[i]);
+		else
+			skb_set_mac_header(skb[i], -ETH_HLEN);
+		__skb_pull(skb[i], doffset);
+	}
+
+	/* setup shinfo.
+	 * mimic bpf_skb_proto_4_to_6, which resets gso_segs and assigns a
+	 * reduced gso_size.
+	 */
+	skb_shinfo(skb[0])->gso_size = 1288;
+	skb_shinfo(skb[0])->gso_type = SKB_GSO_TCPV6 | SKB_GSO_DODGY;
+	skb_shinfo(skb[0])->gso_segs = 0;
+	skb_shinfo(skb[0])->frag_list = skb[1];
+
+	/* adjust skb[0]'s len */
+	skb[0]->len += skb[1]->len;
+	skb[0]->data_len += skb[1]->len;
+	skb[0]->truesize += skb[1]->truesize;
+
+	return skb[0];
+
+err_skb1:
+	kfree_skb(skb[0]);
+err_skb0:
+	return NULL;
+}
+
 struct skb_segment_test {
 	const char *descr;
 	struct sk_buff *(*build_skb)(void);
@@ -6871,6 +6925,15 @@ static struct skb_segment_test skb_segment_tests[] __initconst = {
 		.build_skb = build_test_skb,
 		.features = NETIF_F_SG | NETIF_F_GSO_PARTIAL | NETIF_F_IP_CSUM |
 			    NETIF_F_IPV6_CSUM | NETIF_F_RXCSUM
+	},
+	{
+		.descr = "gso_linear_no_head_frag",
+		.build_skb = build_test_skb_linear_no_head_frag,
+		.features = NETIF_F_SG | NETIF_F_FRAGLIST |
+			    NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_GSO |
+			    NETIF_F_LLTX_BIT | NETIF_F_GRO |
+			    NETIF_F_IPV6_CSUM | NETIF_F_RXCSUM |
+			    NETIF_F_HW_VLAN_STAG_TX_BIT
 	}
 };
 
-- 
2.17.1

Re: [PATCH bpf-next 0/2] test_bpf: Add an skb_segment test for a linear head_frag=0 skb whose gso_size was mangled

[Daniel Borkmann]

On Fri, Oct 25, 2019 at 04:42:21PM +0300, Shmulik Ladkani wrote:
> Add a reproducer test that mimics the input skbs that lead to the BUG_ON
> in skb_segment() which was fixed by commit 3dcbdb134f32 ("net: gso: Fix skb_segment splat when splitting gso_size mangled skb having linear-headed frag_list").
> 
> Shmulik Ladkani (2):
>   test_bpf: Refactor test_skb_segment() to allow testing skb_segment()
>     on numerous different skbs
>   test_bpf: Introduce 'gso_linear_no_head_frag' skb_segment test
> 
>  lib/test_bpf.c | 112 +++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 103 insertions(+), 9 deletions(-)

Applied, thanks!