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Subject[PATCH] Fix kernel panic when calling tcp_v(4/6)_md5_do_lookup
If the following packet flow happen, kernel will panic.
MathineA MathineB
SYN
---------------------->
SYN+ACK
<----------------------
ACK(bad seq)
---------------------->
When a bad seq ACK is received, tcp_v4_md5_do_lookup(skb->sk, ip_hdr(skb)->daddr))
is finally called by tcp_v4_reqsk_send_ack(), but the first parameter(skb->sk) is
NULL at that moment, so kernel panic happens.
This patch fixes this bug.

OOPS output is as following:
[ 302.812793] IP: [<c05cfaa6>] tcp_v4_md5_do_lookup+0x12/0x42
[ 302.817075] Oops: 0000 [#1] SMP
[ 302.819815] Modules linked in: ipv6 loop dm_multipath rtc_cmos rtc_core rtc_lib pcspkr pcnet32 mii i2c_piix4 parport_pc i2c_core parport ac button ata_piix libata dm_mod mptspi mptscsih mptbase scsi_transport_spi sd_mod scsi_mod crc_t10dif ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd [last unloaded: scsi_wait_scan]
[ 302.849946]
[ 302.851198] Pid: 0, comm: swapper Not tainted (2.6.27-rc1-guijf #5)
[ 302.855184] EIP: 0060:[<c05cfaa6>] EFLAGS: 00010296 CPU: 0
[ 302.858296] EIP is at tcp_v4_md5_do_lookup+0x12/0x42
[ 302.861027] EAX: 0000001e EBX: 00000000 ECX: 00000046 EDX: 00000046
[ 302.864867] ESI: ceb69e00 EDI: 1467a8c0 EBP: cf75f180 ESP: c0792e54
[ 302.868333] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
[ 302.871287] Process swapper (pid: 0, ti=c0792000 task=c0712340 task.ti=c0746000)
[ 302.875592] Stack: c06f413a 00000000 cf75f180 ceb69e00 00000000 c05d0d86 000016d0 ceac5400
[ 302.883275] c05d28f8 000016d0 ceb69e00 ceb69e20 681bf6e3 00001000 00000000 0a67a8c0
[ 302.890971] ceac5400 c04250a3 c06f413a c0792eb0 c0792edc cf59a620 cf59a620 cf59a634
[ 302.900140] Call Trace:
[ 302.902392] [<c05d0d86>] tcp_v4_reqsk_send_ack+0x17/0x35
[ 302.907060] [<c05d28f8>] tcp_check_req+0x156/0x372
[ 302.910082] [<c04250a3>] printk+0x14/0x18
[ 302.912868] [<c05d0aa1>] tcp_v4_do_rcv+0x1d3/0x2bf
[ 302.917423] [<c05d26be>] tcp_v4_rcv+0x563/0x5b9
[ 302.920453] [<c05bb20f>] ip_local_deliver_finish+0xe8/0x183
[ 302.923865] [<c05bb10a>] ip_rcv_finish+0x286/0x2a3
[ 302.928569] [<c059e438>] dev_alloc_skb+0x11/0x25
[ 302.931563] [<c05a211f>] netif_receive_skb+0x2d6/0x33a
[ 302.934914] [<d0917941>] pcnet32_poll+0x333/0x680 [pcnet32]
[ 302.938735] [<c05a3b48>] net_rx_action+0x5c/0xfe
[ 302.941792] [<c042856b>] __do_softirq+0x5d/0xc1
[ 302.944788] [<c042850e>] __do_softirq+0x0/0xc1
[ 302.948999] [<c040564b>] do_softirq+0x55/0x88
[ 302.951870] [<c04501b1>] handle_fasteoi_irq+0x0/0xa4
[ 302.954986] [<c04284da>] irq_exit+0x35/0x69
[ 302.959081] [<c0405717>] do_IRQ+0x99/0xae
[ 302.961896] [<c040422b>] common_interrupt+0x23/0x28
[ 302.966279] [<c040819d>] default_idle+0x2a/0x3d
[ 302.969212] [<c0402552>] cpu_idle+0xb2/0xd2
[ 302.972169] =======================
[ 302.974274] Code: fc ff 84 d2 0f 84 df fd ff ff e9 34 fe ff ff 83 c4 0c 5b 5e 5f 5d c3 90 90 57 89 d7 56 53 89 c3 50 68 3a 41 6f c0 e8 e9 55 e5 ff <8b> 93 9c 04 00 00 58 85 d2 59 74 1e 8b 72 10 31 db 31 c9 85 f6
[ 303.011610] EIP: [<c05cfaa6>] tcp_v4_md5_do_lookup+0x12/0x42 SS:ESP 0068:c0792e54
[ 303.018360] Kernel panic - not syncing: Fatal exception in interrupt

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
---
include/net/request_sock.h | 2 +-
net/dccp/dccp.h | 3 ++-
net/dccp/minisocks.c | 3 ++-
net/ipv4/tcp_ipv4.c | 4 ++--
net/ipv4/tcp_minisocks.c | 2 +-
net/ipv6/tcp_ipv6.c | 8 +++++---
6 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index 8d6e991..cac811e 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -33,7 +33,7 @@ struct request_sock_ops {
struct kmem_cache *slab;
int (*rtx_syn_ack)(struct sock *sk,
struct request_sock *req);
- void (*send_ack)(struct sk_buff *skb,
+ void (*send_ack)(struct sock *sk, struct sk_buff *skb,
struct request_sock *req);
void (*send_reset)(struct sock *sk,
struct sk_buff *skb);
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 1c2e3ec..b4bc6e0 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -229,7 +229,8 @@ extern void dccp_v4_send_check(struct sock *sk, int len, struct sk_buff *skb);
extern int dccp_retransmit_skb(struct sock *sk);

extern void dccp_send_ack(struct sock *sk);
-extern void dccp_reqsk_send_ack(struct sk_buff *sk, struct request_sock *rsk);
+extern void dccp_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
+ struct request_sock *rsk);

extern void dccp_send_sync(struct sock *sk, const u64 seq,
const enum dccp_pkt_type pkt_type);
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index 66dca5b..b2804e2 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -296,7 +296,8 @@ int dccp_child_process(struct sock *parent, struct sock *child,

EXPORT_SYMBOL_GPL(dccp_child_process);

-void dccp_reqsk_send_ack(struct sk_buff *skb, struct request_sock *rsk)
+void dccp_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
+ struct request_sock *rsk)
{
DCCP_BUG("DCCP-ACK packets are never sent in LISTEN/RESPOND state");
}
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 91a8cfd..44c1e93 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -687,14 +687,14 @@ static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb)
inet_twsk_put(tw);
}

-static void tcp_v4_reqsk_send_ack(struct sk_buff *skb,
+static void tcp_v4_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
struct request_sock *req)
{
tcp_v4_send_ack(skb, tcp_rsk(req)->snt_isn + 1,
tcp_rsk(req)->rcv_isn + 1, req->rcv_wnd,
req->ts_recent,
0,
- tcp_v4_md5_do_lookup(skb->sk, ip_hdr(skb)->daddr));
+ tcp_v4_md5_do_lookup(sk, ip_hdr(skb)->daddr));
}

/*
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 204c421..6d286f5 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -609,7 +609,7 @@ struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb,
tcp_rsk(req)->rcv_isn + 1, tcp_rsk(req)->rcv_isn + 1 + req->rcv_wnd)) {
/* Out of window: send ACK and drop. */
if (!(flg & TCP_FLAG_RST))
- req->rsk_ops->send_ack(skb, req);
+ req->rsk_ops->send_ack(sk, skb, req);
if (paws_reject)
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
return NULL;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 78185a4..5b90b36 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -69,7 +69,8 @@
#include <linux/scatterlist.h>

static void tcp_v6_send_reset(struct sock *sk, struct sk_buff *skb);
-static void tcp_v6_reqsk_send_ack(struct sk_buff *skb, struct request_sock *req);
+static void tcp_v6_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
+ struct request_sock *req);

static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb);

@@ -1138,10 +1139,11 @@ static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
inet_twsk_put(tw);
}

-static void tcp_v6_reqsk_send_ack(struct sk_buff *skb, struct request_sock *req)
+static void tcp_v6_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
+ struct request_sock *req)
{
tcp_v6_send_ack(skb, tcp_rsk(req)->snt_isn + 1, tcp_rsk(req)->rcv_isn + 1, req->rcv_wnd, req->ts_recent,
- tcp_v6_md5_do_lookup(skb->sk, &ipv6_hdr(skb)->daddr));
+ tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr));
}


--
1.5.3



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