* [PATCH net] ip: frags: fix crash in ip_do_fragment()
@ 2018-09-06 17:50 Taehee Yoo
2018-09-06 18:06 ` Eric Dumazet
0 siblings, 1 reply; 4+ messages in thread
From: Taehee Yoo @ 2018-09-06 17:50 UTC (permalink / raw)
To: davem, posk, netdev; +Cc: ap420073, pablo, fw, edumazet
A kernel crash occurrs when defragmented packet is fragmented
in ip_do_fragment().
In defragment routine, skb_orphan() is called and
skb->ip_defrag_offset is set. but skb->sk and
skb->ip_defrag_offset are same union member. so that
frag->sk is not NULL.
Hence crash occurrs in skb->sk check routine in ip_do_fragment() when
defragmented packet is fragmented.
test commands:
%iptables -t nat -I POSTROUTING -j MASQUERADE
%hping3 192.168.4.2 -s 1000 -p 2000 -d 60000
splat looks like:
[ 261.069429] kernel BUG at net/ipv4/ip_output.c:636!
[ 261.075753] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
[ 261.083854] CPU: 1 PID: 1349 Comm: hping3 Not tainted 4.19.0-rc2+ #3
[ 261.100977] RIP: 0010:ip_do_fragment+0x1613/0x2600
[ 261.106945] Code: e8 e2 38 e3 fe 4c 8b 44 24 18 48 8b 74 24 08 e9 92 f6 ff ff 80 3c 02 00 0f 85 da 07 00 00 48 8b b5 d0 00 00 00 e9 25 f6 ff ff <0f> 0b 0f 0b 44 8b 54 24 58 4c 8b 4c 24 18 4c 8b 5c 24 60 4c 8b 6c
[ 261.127015] RSP: 0018:ffff8801031cf2c0 EFLAGS: 00010202
[ 261.134156] RAX: 1ffff1002297537b RBX: ffffed0020639e6e RCX: 0000000000000004
[ 261.142156] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880114ba9bd8
[ 261.150157] RBP: ffff880114ba8a40 R08: ffffed0022975395 R09: ffffed0022975395
[ 261.158157] R10: 0000000000000001 R11: ffffed0022975394 R12: ffff880114ba9ca4
[ 261.166159] R13: 0000000000000010 R14: ffff880114ba9bc0 R15: dffffc0000000000
[ 261.174169] FS: 00007fbae2199700(0000) GS:ffff88011b400000(0000) knlGS:0000000000000000
[ 261.183012] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 261.189013] CR2: 00005579244fe000 CR3: 0000000119bf4000 CR4: 00000000001006e0
[ 261.198158] Call Trace:
[ 261.199018] ? dst_output+0x180/0x180
[ 261.205011] ? save_trace+0x300/0x300
[ 261.209018] ? ip_copy_metadata+0xb00/0xb00
[ 261.213034] ? sched_clock_local+0xd4/0x140
[ 261.218158] ? kill_l4proto+0x120/0x120 [nf_conntrack]
[ 261.223014] ? rt_cpu_seq_stop+0x10/0x10
[ 261.227014] ? find_held_lock+0x39/0x1c0
[ 261.233008] ip_finish_output+0x51d/0xb50
[ 261.237006] ? ip_fragment.constprop.56+0x220/0x220
[ 261.243011] ? nf_ct_l4proto_register_one+0x5b0/0x5b0 [nf_conntrack]
[ 261.250152] ? rcu_is_watching+0x77/0x120
[ 261.255010] ? nf_nat_ipv4_out+0x1e/0x2b0 [nf_nat_ipv4]
[ 261.261033] ? nf_hook_slow+0xb1/0x160
[ 261.265007] ip_output+0x1c7/0x710
[ 261.269005] ? ip_mc_output+0x13f0/0x13f0
[ 261.273002] ? __local_bh_enable_ip+0xe9/0x1b0
[ 261.278152] ? ip_fragment.constprop.56+0x220/0x220
[ 261.282996] ? nf_hook_slow+0xb1/0x160
[ 261.287007] raw_sendmsg+0x21f9/0x4420
[ 261.291008] ? dst_output+0x180/0x180
[ 261.297003] ? sched_clock_cpu+0x126/0x170
[ 261.301003] ? find_held_lock+0x39/0x1c0
[ 261.306155] ? stop_critical_timings+0x420/0x420
[ 261.311004] ? check_flags.part.36+0x450/0x450
[ 261.315005] ? _raw_spin_unlock_irq+0x29/0x40
[ 261.320995] ? _raw_spin_unlock_irq+0x29/0x40
[ 261.326142] ? cyc2ns_read_end+0x10/0x10
[ 261.330139] ? raw_bind+0x280/0x280
[ 261.334138] ? sched_clock_cpu+0x126/0x170
[ 261.338995] ? check_flags.part.36+0x450/0x450
[ 261.342991] ? __lock_acquire+0x4500/0x4500
[ 261.348994] ? inet_sendmsg+0x11c/0x500
[ 261.352989] ? dst_output+0x180/0x180
[ 261.357012] inet_sendmsg+0x11c/0x500
[ ... ]
Fixes: fa0f527358bd ("ip: use rb trees for IP frag queue.")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
---
include/linux/skbuff.h | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 17a13e4785fc..2eb115be5bf6 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -676,16 +676,13 @@ struct sk_buff {
* UDP receive path is one user.
*/
unsigned long dev_scratch;
+ int ip_defrag_offset;
};
};
struct rb_node rbnode; /* used in netem, ip4 defrag, and tcp stack */
struct list_head list;
};
-
- union {
- struct sock *sk;
- int ip_defrag_offset;
- };
+ struct sock *sk;
union {
ktime_t tstamp;
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH net] ip: frags: fix crash in ip_do_fragment()
2018-09-06 17:50 [PATCH net] ip: frags: fix crash in ip_do_fragment() Taehee Yoo
@ 2018-09-06 18:06 ` Eric Dumazet
2018-09-06 18:23 ` Eric Dumazet
0 siblings, 1 reply; 4+ messages in thread
From: Eric Dumazet @ 2018-09-06 18:06 UTC (permalink / raw)
To: ap420073
Cc: David Miller, Peter Oskolkov, netdev, Pablo Neira Ayuso,
Florian Westphal
On Thu, Sep 6, 2018 at 10:51 AM Taehee Yoo <ap420073@gmail.com> wrote:
>
> A kernel crash occurrs when defragmented packet is fragmented
> in ip_do_fragment().
> In defragment routine, skb_orphan() is called and
> skb->ip_defrag_offset is set. but skb->sk and
> skb->ip_defrag_offset are same union member. so that
> frag->sk is not NULL.
> Hence crash occurrs in skb->sk check routine in ip_do_fragment() when
> defragmented packet is fragmented.
Have you tested this patch ?
Moving back ip_defrag_offset is conflicting with the rbnode !
A more correct fix would be to properly clear skb->sk at reassembly.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] ip: frags: fix crash in ip_do_fragment()
2018-09-06 18:06 ` Eric Dumazet
@ 2018-09-06 18:23 ` Eric Dumazet
2018-09-06 18:48 ` Taehee Yoo
0 siblings, 1 reply; 4+ messages in thread
From: Eric Dumazet @ 2018-09-06 18:23 UTC (permalink / raw)
To: ap420073
Cc: David Miller, Peter Oskolkov, netdev, Pablo Neira Ayuso,
Florian Westphal
On Thu, Sep 6, 2018 at 11:06 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Thu, Sep 6, 2018 at 10:51 AM Taehee Yoo <ap420073@gmail.com> wrote:
> >
> > A kernel crash occurrs when defragmented packet is fragmented
> > in ip_do_fragment().
> > In defragment routine, skb_orphan() is called and
> > skb->ip_defrag_offset is set. but skb->sk and
> > skb->ip_defrag_offset are same union member. so that
> > frag->sk is not NULL.
> > Hence crash occurrs in skb->sk check routine in ip_do_fragment() when
> > defragmented packet is fragmented.
>
> Have you tested this patch ?
>
> Moving back ip_defrag_offset is conflicting with the rbnode !
>
> A more correct fix would be to properly clear skb->sk at reassembly.
Something like that :
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 88281fbce88ce8f1062b99594665766c2a5f5b74..e7227128df2c8fd54727c234f76043133809bd1e
100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -599,6 +599,7 @@ static int ip_frag_reasm(struct ipq *qp, struct
sk_buff *skb,
nextp = &fp->next;
fp->prev = NULL;
memset(&fp->rbnode, 0, sizeof(fp->rbnode));
+ fp->sk = NULL;
head->data_len += fp->len;
head->len += fp->len;
if (head->ip_summed != fp->ip_summed)
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] ip: frags: fix crash in ip_do_fragment()
2018-09-06 18:23 ` Eric Dumazet
@ 2018-09-06 18:48 ` Taehee Yoo
0 siblings, 0 replies; 4+ messages in thread
From: Taehee Yoo @ 2018-09-06 18:48 UTC (permalink / raw)
To: Eric Dumazet
Cc: David Miller, Peter Oskolkov, netdev, Pablo Neira Ayuso,
Florian Westphal
2018-09-07 3:23 GMT+09:00 Eric Dumazet <edumazet@google.com>:
> On Thu, Sep 6, 2018 at 11:06 AM Eric Dumazet <edumazet@google.com> wrote:
>>
>> On Thu, Sep 6, 2018 at 10:51 AM Taehee Yoo <ap420073@gmail.com> wrote:
>> >
>> > A kernel crash occurrs when defragmented packet is fragmented
>> > in ip_do_fragment().
>> > In defragment routine, skb_orphan() is called and
>> > skb->ip_defrag_offset is set. but skb->sk and
>> > skb->ip_defrag_offset are same union member. so that
>> > frag->sk is not NULL.
>> > Hence crash occurrs in skb->sk check routine in ip_do_fragment() when
>> > defragmented packet is fragmented.
>>
>> Have you tested this patch ?
>>
>> Moving back ip_defrag_offset is conflicting with the rbnode !
>>
>> A more correct fix would be to properly clear skb->sk at reassembly.
>
> Something like that :
>
> diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
> index 88281fbce88ce8f1062b99594665766c2a5f5b74..e7227128df2c8fd54727c234f76043133809bd1e
> 100644
> --- a/net/ipv4/ip_fragment.c
> +++ b/net/ipv4/ip_fragment.c
> @@ -599,6 +599,7 @@ static int ip_frag_reasm(struct ipq *qp, struct
> sk_buff *skb,
> nextp = &fp->next;
> fp->prev = NULL;
> memset(&fp->rbnode, 0, sizeof(fp->rbnode));
> + fp->sk = NULL;
> head->data_len += fp->len;
> head->len += fp->len;
> if (head->ip_summed != fp->ip_summed)
Hi Eric!
Oh I'm sorry, I realized that ip_defrag_offset would be conflicting
with the rbnode just now
So, this patch should be dropped.
And I will make v2 patch regard you suggested!
Thank you for review and suggestion!
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2018-09-06 23:25 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2018-09-06 17:50 [PATCH net] ip: frags: fix crash in ip_do_fragment() Taehee Yoo
2018-09-06 18:06 ` Eric Dumazet
2018-09-06 18:23 ` Eric Dumazet
2018-09-06 18:48 ` Taehee Yoo
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).