test_bpf: Add an skb_segment test for a non linear frag_list whose head_frag=1 and gso_size was mangled

Commit Message

Fred Li May 17, 2024, 3:40 p.m. UTC

The patch was based on kernel 6.6.8, the skb properties as
mentioned in [1]. This test will cause system crash without
the patch described in [1].

[1] https://lore.kernel.org/netdev/[e-mail]/

Signed-off-by: Fred Li <[e-mail]>
---
 lib/test_bpf.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

Comments

Fred Li May 27, 2024, 1:59 p.m. UTC | #1

For kernel 6.6.8, when sg is true and skb_headlen(list_skb) != len, it also has 
chance run into this BUG_ON() line 4548.
'''
4544                 hsize = skb_headlen(head_skb) - offset;
4545 
4546                 if (hsize <= 0 && i >= nfrags && skb_headlen(list_skb) &&
4547                     (skb_headlen(list_skb) == len || sg)) {
4548                         BUG_ON(skb_headlen(list_skb) > len);
4549 
4550                         nskb = skb_clone(list_skb, GFP_ATOMIC);
'''

As commit 9e4b7a99a03a("net: gso: fix panic on frag_list with mixed head alloc types")
said. It walk the frag_list in skb_segment and clear NETIF_F_SG when there is non head_frag 
skb. 

But for frag_list only with one head_frag, NETIF_F_SG was not cleared, if skb_headlen(list_skb) != len,
in this case, maybe we can fix it with run into segment as commit 13acc94eff122(net: permit skb_segment on 
head_frag frag_list skb). 

Any suggestions for resolving this issue.

Thanks

Fred Li

Patch

diff --git a/lib/test_bpf.c b/lib/test_bpf.c
index ecde42162..a38d2d09c 100644
--- a/lib/test_bpf.c
+++ b/lib/test_bpf.c
@@ -14706,6 +14706,63 @@  static __init struct sk_buff *build_test_skb_linear_no_head_frag(void)
 	return NULL;
 }
 
+static __init struct sk_buff *build_test_skb_head_frag(void)
+{
+	u32 headroom = 192, doffset = 66, alloc_size = 1536;
+	struct sk_buff *skb[2];
+	struct page *page[17];
+	int i, data_size = 125;
+	int j;
+
+	skb[0] = dev_alloc_skb(headroom + alloc_size);
+	if (!skb[0])
+		return NULL;
+
+	skb_reserve(skb[0], headroom + doffset);
+	skb_put(skb[0], data_size);
+	skb[0]->mac_header = 192;
+
+	skb[0]->protocol = htons(ETH_P_IP);
+	skb[0]->network_header = 206;
+
+	for (i = 0; i < 17; i++) {
+		page[i] = alloc_page(GFP_KERNEL);
+		if (!page[i])
+			goto err_page;
+
+		skb_add_rx_frag(skb[0], i, page[i], 0, data_size, data_size);
+	}
+
+	skb[1] = dev_alloc_skb(headroom + alloc_size);
+	if (!skb[1])
+		goto err_page;
+
+	skb_reserve(skb[1], headroom + doffset);
+	skb_put(skb[1], data_size);
+
+	/* setup shinfo */
+	skb_shinfo(skb[0])->gso_size = 75;
+	skb_shinfo(skb[0])->gso_type = SKB_GSO_TCPV4;
+	skb_shinfo(skb[0])->gso_type |= SKB_GSO_UDP_TUNNEL|SKB_GSO_TCP_FIXEDID|SKB_GSO_DODGY;
+	skb_shinfo(skb[0])->gso_segs = 0;
+	skb_shinfo(skb[0])->frag_list = skb[1];
+	skb_shinfo(skb[0])->hwtstamps.hwtstamp = 1000;
+
+	/* 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_page:
+	kfree_skb(skb[0]);
+	for (j = 0; j < i; j++)
+		__free_page(page[j]);
+
+	return NULL;
+}
+
 struct skb_segment_test {
 	const char *descr;
 	struct sk_buff *(*build_skb)(void);
@@ -14727,6 +14784,13 @@  static struct skb_segment_test skb_segment_tests[] __initconst = {
 			    NETIF_F_LLTX | NETIF_F_GRO |
 			    NETIF_F_IPV6_CSUM | NETIF_F_RXCSUM |
 			    NETIF_F_HW_VLAN_STAG_TX
+	},
+	{
+		.descr = "gso_with_head_frag",
+		.build_skb = build_test_skb_head_frag,
+		.features = NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SHIFT |
+			    NETIF_F_TSO_ECN | NETIF_F_TSO_MANGLEID | NETIF_F_TSO6 |
+			    NETIF_F_GSO_SCTP | NETIF_F_GSO_UDP_L4 | NETIF_F_GSO_FRAGLIST
 	}
 };