On 2023-05-03 09:35, Xin Long wrote:
On Tue, May 2, 2023 at 11:31 PM Tung Quang Nguyen
<tung.q.ngu...@dektech.com.au> wrote:
When doing link mtu negotiation, a malicious peer may send Activate msg
with a very small mtu, e.g. 4 in Shuang's testing, without checking for
the minimum mtu, l->mtu will be set to 4 in tipc_link_proto_rcv(), then
n->links[bearer_id].mtu is set to 4294967228, which is a overflow of
'4 - INT_H_SIZE - EMSG_OVERHEAD' in tipc_link_mss().
With tipc_link.mtu = 4, tipc_link_xmit() kept printing the warning:
tipc: Too large msg, purging xmit list 1 5 0 40 4!
tipc: Too large msg, purging xmit list 1 15 0 60 4!
And with tipc_link_entry.mtu 4294967228, a huge skb was allocated in
named_distribute(), and when purging it in tipc_link_xmit(), a crash
was even caused:
general protection fault, probably for non-canonical address
0x2100001011000dd: 0000 [#1] PREEMPT SMP PTI
CPU: 0 PID: 0 Comm: swapper/0 Kdump: loaded Not tainted 6.3.0.neta #19
RIP: 0010:kfree_skb_list_reason+0x7e/0x1f0
Call Trace:
<IRQ>
skb_release_data+0xf9/0x1d0
kfree_skb_reason+0x40/0x100
tipc_link_xmit+0x57a/0x740 [tipc]
tipc_node_xmit+0x16c/0x5c0 [tipc]
tipc_named_node_up+0x27f/0x2c0 [tipc]
tipc_node_write_unlock+0x149/0x170 [tipc]
tipc_rcv+0x608/0x740 [tipc]
tipc_udp_recv+0xdc/0x1f0 [tipc]
udp_queue_rcv_one_skb+0x33e/0x620
udp_unicast_rcv_skb.isra.72+0x75/0x90
__udp4_lib_rcv+0x56d/0xc20
ip_protocol_deliver_rcu+0x100/0x2d0
This patch fixes it by checking the new mtu against tipc_bearer_min_mtu(),
and not updating mtu if it is too small.
v1->v2:
- do the msg_max check against the min MTU early, as Tung suggested.
Please move above version change comment to after "---".
I think it's correct to NOT use ''---' for version changes, see the
comment from davem:
https://lore.kernel.org/netdev/20160415.172858.253625178036493951.da...@davemloft.net/
unless there are some new rules I missed.
I have not seen this one before, and I disagree with David here. Many of
the changes
between versions are trivial, and some comments even incomprehensible
once the patch has
been applied.
I have always put them after the "---" comment, and I will continue to
do so until David starts
rejecting such patches.
But ok, do as you find right.
///jon
Thanks.
Fixes: ed193ece2649 ("tipc: simplify link mtu negotiation")
Reported-by: Shuang Li <shu...@redhat.com>
Signed-off-by: Xin Long <lucien....@gmail.com>
---
net/tipc/link.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/net/tipc/link.c b/net/tipc/link.c
index b3ce24823f50..2eff1c7949cb 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -2200,7 +2200,7 @@ static int tipc_link_proto_rcv(struct tipc_link *l,
struct sk_buff *skb,
struct tipc_msg *hdr = buf_msg(skb);
struct tipc_gap_ack_blks *ga = NULL;
bool reply = msg_probe(hdr), retransmitted = false;
- u32 dlen = msg_data_sz(hdr), glen = 0;
+ u32 dlen = msg_data_sz(hdr), glen = 0, msg_max;
u16 peers_snd_nxt = msg_next_sent(hdr);
u16 peers_tol = msg_link_tolerance(hdr);
u16 peers_prio = msg_linkprio(hdr);
@@ -2239,6 +2239,9 @@ static int tipc_link_proto_rcv(struct tipc_link *l,
struct sk_buff *skb,
switch (mtyp) {
case RESET_MSG:
case ACTIVATE_MSG:
+ msg_max = msg_max_pkt(hdr);
+ if (msg_max < tipc_bearer_min_mtu(l->net, l->bearer_id))
+ break;
/* Complete own link name with peer's interface name */
if_name = strrchr(l->name, ':') + 1;
if (sizeof(l->name) - (if_name - l->name) <= TIPC_MAX_IF_NAME)
@@ -2283,8 +2286,8 @@ static int tipc_link_proto_rcv(struct tipc_link *l,
struct sk_buff *skb,
l->peer_session = msg_session(hdr);
l->in_session = true;
l->peer_bearer_id = msg_bearer_id(hdr);
- if (l->mtu > msg_max_pkt(hdr))
- l->mtu = msg_max_pkt(hdr);
+ if (l->mtu > msg_max)
+ l->mtu = msg_max;
break;
case STATE_MSG:
--
2.39.1
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