[patch 20/37] {nfnetlink, ip, ip6}_queue: fix skb_over_panic whenenlarging packets

From: Greg KH
Date: Tue May 13 2008 - 16:20:22 EST

2.6.25-stable review patch. If anyone has any objections, please let us
know.

------------------
From: Arnaud Ebalard <arno@xxxxxxxxxxxx>

[NETFILTER]: {nfnetlink,ip,ip6}_queue: fix skb_over_panic when enlarging packets

From: Arnaud Ebalard <arno@xxxxxxxxxxxx>

Upstream commit 9a732ed6d:

While reinjecting *bigger* modified versions of IPv6 packets using
libnetfilter_queue, things work fine on a 2.6.24 kernel (2.6.22 too)
but I get the following on recents kernels (2.6.25, trace below is
against today's net-2.6 git tree):

skb_over_panic: text:c04fddb0 len:696 put:632 head:f7592c00 data:f7592c00 tail:0xf7592eb8 end:0xf7592e80 dev:eth0
------------[ cut here ]------------
invalid opcode: 0000 [#1] PREEMPT
Process sendd (pid: 3657, ti=f6014000 task=f77c31d0 task.ti=f6014000)
Stack: c071e638 c04fddb0 000002b8 00000278 f7592c00 f7592c00 f7592eb8 f7592e80
f763c000 f6bc5200 f7592c40 f6015c34 c04cdbfc f6bc5200 00000278 f6015c60
c04fddb0 00000020 f72a10c0 f751b420 00000001 0000000a 000002b8 c065582c
Call Trace:
[<c04fddb0>] ? nfqnl_recv_verdict+0x1c0/0x2e0
[<c04cdbfc>] ? skb_put+0x3c/0x40
[<c04fddb0>] ? nfqnl_recv_verdict+0x1c0/0x2e0
[<c04fd115>] ? nfnetlink_rcv_msg+0xf5/0x160
[<c04fd03e>] ? nfnetlink_rcv_msg+0x1e/0x160
[<c04fd020>] ? nfnetlink_rcv_msg+0x0/0x160
[<c04f8ed7>] ? netlink_rcv_skb+0x77/0xa0
[<c04fcefc>] ? nfnetlink_rcv+0x1c/0x30
[<c04f8c73>] ? netlink_unicast+0x243/0x2b0
[<c04cfaba>] ? memcpy_fromiovec+0x4a/0x70
[<c04f9406>] ? netlink_sendmsg+0x1c6/0x270
[<c04c8244>] ? sock_sendmsg+0xc4/0xf0
[<c011970d>] ? set_next_entity+0x1d/0x50
[<c0133a80>] ? autoremove_wake_function+0x0/0x40
[<c0118f9e>] ? __wake_up_common+0x3e/0x70
[<c0342fbf>] ? n_tty_receive_buf+0x34f/0x1280
[<c011d308>] ? __wake_up+0x68/0x70
[<c02cea47>] ? copy_from_user+0x37/0x70
[<c04cfd7c>] ? verify_iovec+0x2c/0x90
[<c04c837a>] ? sys_sendmsg+0x10a/0x230
[<c011967a>] ? __dequeue_entity+0x2a/0xa0
[<c011970d>] ? set_next_entity+0x1d/0x50
[<c0345397>] ? pty_write+0x47/0x60
[<c033d59b>] ? tty_default_put_char+0x1b/0x20
[<c011d2e9>] ? __wake_up+0x49/0x70
[<c033df99>] ? tty_ldisc_deref+0x39/0x90
[<c033ff20>] ? tty_write+0x1a0/0x1b0
[<c04c93af>] ? sys_socketcall+0x7f/0x260
[<c0102ff9>] ? sysenter_past_esp+0x6a/0x91
[<c05f0000>] ? snd_intel8x0m_probe+0x270/0x6e0
=======================
Code: 00 00 89 5c 24 14 8b 98 9c 00 00 00 89 54 24 0c 89 5c 24 10 8b 40 50 89 4c 24 04 c7 04 24 38 e6 71 c0 89 44 24 08 e8 c4 46 c5 ff <0f> 0b eb fe 55 89 e5 56 89 d6 53 89 c3 83 ec 0c 8b 40 50 39 d0
EIP: [<c04ccdfc>] skb_over_panic+0x5c/0x60 SS:ESP 0068:f6015bf8

Looking at the code, I ended up in nfq_mangle() function (called by
nfqnl_recv_verdict()) which performs a call to skb_copy_expand() due to
the increased size of data passed to the function. AFAICT, it should ask
for 'diff' instead of 'diff - skb_tailroom(e->skb)'. Because the
resulting sk_buff has not enough space to support the skb_put(skb, diff)
call a few lines later, this results in the call to skb_over_panic().

The patch below asks for allocation of a copy with enough space for
mangled packet and the same amount of headroom as old sk_buff. While
looking at how the regression appeared (e2b58a67), I noticed the same
pattern in ipq_mangle_ipv6() and ipq_mangle_ipv4(). The patch corrects
those locations too.

Tested with bigger reinjected IPv6 packets (nfqnl_mangle() path), things
are ok (2.6.25 and today's net-2.6 git tree).

Signed-off-by: Arnaud Ebalard <arno@xxxxxxxxxxxx>
Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>


---
net/ipv4/netfilter/ip_queue.c | 5 ++---
net/ipv6/netfilter/ip6_queue.c | 5 ++---
net/netfilter/nfnetlink_queue.c | 5 ++---
3 files changed, 6 insertions(+), 9 deletions(-)

--- a/net/ipv4/netfilter/ip_queue.c
+++ b/net/ipv4/netfilter/ip_queue.c
@@ -296,9 +296,8 @@ ipq_mangle_ipv4(ipq_verdict_msg_t *v, st
if (v->data_len > 0xFFFF)
return -EINVAL;
if (diff > skb_tailroom(e->skb)) {
- nskb = skb_copy_expand(e->skb, 0,
- diff - skb_tailroom(e->skb),
- GFP_ATOMIC);
+ nskb = skb_copy_expand(e->skb, skb_headroom(e->skb),
+ diff, GFP_ATOMIC);
if (!nskb) {
printk(KERN_WARNING "ip_queue: error "
"in mangle, dropping packet\n");
--- a/net/ipv6/netfilter/ip6_queue.c
+++ b/net/ipv6/netfilter/ip6_queue.c
@@ -298,9 +298,8 @@ ipq_mangle_ipv6(ipq_verdict_msg_t *v, st
if (v->data_len > 0xFFFF)
return -EINVAL;
if (diff > skb_tailroom(e->skb)) {
- nskb = skb_copy_expand(e->skb, 0,
- diff - skb_tailroom(e->skb),
- GFP_ATOMIC);
+ nskb = skb_copy_expand(e->skb, skb_headroom(e->skb),
+ diff, GFP_ATOMIC);
if (!nskb) {
printk(KERN_WARNING "ip6_queue: OOM "
"in mangle, dropping packet\n");
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -454,9 +454,8 @@ nfqnl_mangle(void *data, int data_len, s
if (data_len > 0xFFFF)
return -EINVAL;
if (diff > skb_tailroom(e->skb)) {
- nskb = skb_copy_expand(e->skb, 0,
- diff - skb_tailroom(e->skb),
- GFP_ATOMIC);
+ nskb = skb_copy_expand(e->skb, skb_headroom(e->skb),
+ diff, GFP_ATOMIC);
if (!nskb) {
printk(KERN_WARNING "nf_queue: OOM "
"in mangle, dropping packet\n");

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