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bpf, testing: Introduce 'gso_linear_no_head_frag' skb_segment test

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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 3dcbdb134f ("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>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191025134223.2761-3-shmulik.ladkani@gmail.com
This commit is contained in:
Shmulik Ladkani 2019-10-25 16:42:23 +03:00 committed by Daniel Borkmann
parent af21c717f4
commit cf204a7183
1 changed files with 63 additions and 0 deletions
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63
lib/test_bpf.c
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@ -6859,6 +6859,60 @@ err_page0:
return NULL; 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 { struct skb_segment_test {
const char *descr; const char *descr;
struct sk_buff *(*build_skb)(void); struct sk_buff *(*build_skb)(void);
@ -6871,6 +6925,15 @@ static struct skb_segment_test skb_segment_tests[] __initconst = {
.build_skb = build_test_skb, .build_skb = build_test_skb,
.features = NETIF_F_SG | NETIF_F_GSO_PARTIAL | NETIF_F_IP_CSUM | .features = NETIF_F_SG | NETIF_F_GSO_PARTIAL | NETIF_F_IP_CSUM |
NETIF_F_IPV6_CSUM | NETIF_F_RXCSUM 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
} }
}; };