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Date: Mon, 22 Feb 2010 14:44:48 -0800
From: "Stephens, Allan" <allan.stephens@...driver.com>
To: "Neil Horman" <nhorman@...driver.com>, <netdev@...r.kernel.org>
Cc: <per.liden@...csson.com>, <jon.maloy@...csson.com>,
<tipc-discussion@...ts.sourceforge.net>, <davem@...emloft.net>
Subject: RE: [PATCH]: tipc: Fix oops on send prior to entering networked mode
Hi Neil:
Good work on spotting this bug, and in tracking down the cause. I took
a look at your patch, but there are a couple of problems I can see with
the approach you've taken to fix things:
1) The check you've added to send_msg() in net/tipc/socket.c will help
prevent things from blowing up if the message sender is using an AF_MIPC
socket from user space, but it won't help prevent a similar oops if an
"application" uses TIPC's native API to send a message directly from
kernel space.
2) The other change you made to defer setting tipc_mode to TIPC_NET_MODE
will cause problems if TIPC has to bail out during tipc_net_start()
because of problems. Specifically, the ensuing call to tipc_net_stop()
won't get a chance to clean up any partial initialization that got done
prior to the initialization problem, which could result in memory leaks.
Fortunately, I think there's a relatively easy solution. Since TIPC
always needs to call tipc_node_select() in order to send an off-node
message, you should be able to add the necessary error checking there.
I'm thinking of something along the lines of:
static inline struct tipc_node *tipc_node_select(u32 addr, u32 selector)
{
if (likely(in_own_cluster(addr)))
return tipc_local_nodes ?
tipc_local_nodes[tipc_node(addr)] : NULL;
return tipc_net->zones ? tipc_node_select_next_hop(addr,
selector) : NULL;
}
Please give this a try and let us know how things go.
Regards,
Al
> -----Original Message-----
> From: Neil Horman [mailto:nhorman@...driver.com]
> Sent: Friday, February 19, 2010 2:41 PM
> To: netdev@...r.kernel.org
> Cc: per.liden@...csson.com; jon.maloy@...csson.com; Stephens,
> Allan; tipc-discussion@...ts.sourceforge.net;
> davem@...emloft.net; nhorman@...driver.com
> Subject: [PATCH]: tipc: Fix oops on send prior to entering
> networked mode
>
> Fix TIPC to disallow sending to remote addresses prior to
> entering NET_MODE
>
> user programs can oops the kernel by sending datagrams via
> AF_TIPC prior to entering networked mode. The following
> backtrace has been observed:
>
> ID: 13459 TASK: ffff810014640040 CPU: 0 COMMAND: "tipc-client"
> #0 [ffff81002d9a5810] crash_kexec at ffffffff800ac5b9
> #1 [ffff81002d9a58d0] __die at ffffffff80065127
> #2 [ffff81002d9a5910] do_page_fault at ffffffff80066da7
> #3 [ffff81002d9a5a00] error_exit at ffffffff8005dde9
> [exception RIP: tipc_node_select_next_hop+90]
> RIP: ffffffff8869d3c3 RSP: ffff81002d9a5ab8 RFLAGS: 00010202
> RAX: 0000000000000001 RBX: 0000000000000001 RCX: 0000000000000001
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000001001001
> RBP: 0000000001001001 R8: 0074736575716552 R9: 0000000000000000
> R10: ffff81003fbd0680 R11: 00000000000000c8 R12: 0000000000000008
> R13: 0000000000000001 R14: 0000000000000001 R15: ffff810015c6ca00
> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
> #4 [ffff81002d9a5ab0] tipc_node_select_next_hop at ffffffff8869d3b1
> #5 [ffff81002d9a5ae0] tipc_link_send_sections_fast at ffffffff88698558
> #6 [ffff81002d9a5be0] tipc_forward2port at ffffffff8869eb1d
> #7 [ffff81002d9a5c10] tipc_send2port at ffffffff8869eb79
> #8 [ffff81002d9a5c30] send_msg at ffffffff886a1d0b
> #9 [ffff81002d9a5cb0] sock_sendmsg at ffffffff80055261
> RIP: 0000003cbd8d49a3 RSP: 00007fffc84e0be8 RFLAGS: 00010206
> RAX: 000000000000002c RBX: ffffffff8005d116 RCX: 0000000000000000
> RDX: 0000000000000008 RSI: 00007fffc84e0c00 RDI: 0000000000000003
> RBP: 0000000000000000 R8: 00007fffc84e0c10 R9: 0000000000000010
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fffc84e0d10 R14: 0000000000000000 R15: 00007fffc84e0c30
> ORIG_RAX: 000000000000002c CS: 0033 SS: 002b
>
> What happens is that, when the tipc module in inserted it
> enters a standalone node mode in which communication to its
> own address is allowed <0.0.0> but not to other addresses,
> since the appropriate data structures have not been allocated
> yet (specifically the tipc_net pointer). There is nothing
> stopping a client from trying to send such a message however,
> and if that happens, we attempt to dereference tipc_net.zones
> while the pointer is still NULL, and explode. The fix is to
> add a check at the start of the send_msg path to ensure that
> we've allocated the tipc_net pointers and entered networked
> mode prior to allowing a send to any destination other than
> our loopback address.
>
> This patch has received minimal testing, but fixes the issue.
> Through reviews are appreciated.
>
> Signed-off-by: Neil Horman <nhorman@...driver.com>
>
> CC: Per Liden <per.liden@...csson.com>
> CC: Jon Maloy <jon.maloy@...csson.com>
> CC: Allan Stephens <allan.stephens@...driver.com>
> CC: David S. Miller <davem@...emloft.net>
> CC: Neil Horman <nhorman@...driver.com>
> CC: tipc-discussion@...ts.sourceforge.net
>
>
> net.c | 2 +-
> socket.c | 4 ++++
> 2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/net/tipc/net.c b/net/tipc/net.c index
> 7906608..512b33c 100644
> --- a/net/tipc/net.c
> +++ b/net/tipc/net.c
> @@ -278,7 +278,6 @@ int tipc_net_start(u32 addr)
> tipc_cfg_stop();
>
> tipc_own_addr = addr;
> - tipc_mode = TIPC_NET_MODE;
> tipc_named_reinit();
> tipc_port_reinit();
>
> @@ -289,6 +288,7 @@ int tipc_net_start(u32 addr)
> return res;
> }
>
> + tipc_mode = TIPC_NET_MODE;
> tipc_k_signal((Handler)tipc_subscr_start, 0);
> tipc_k_signal((Handler)tipc_cfg_init, 0);
>
> diff --git a/net/tipc/socket.c b/net/tipc/socket.c index
> 1ea64f0..45229fd 100644
> --- a/net/tipc/socket.c
> +++ b/net/tipc/socket.c
> @@ -526,6 +526,10 @@ static int send_msg(struct kiocb *iocb,
> struct socket *sock,
> if (iocb)
> lock_sock(sk);
>
> + if ((tipc_mode != TIPC_NET_MODE) &&
> + (dest->addr.name.domain != tipc_own_addr))
> + return -EHOSTUNREACH;
> +
> needs_conn = (sock->state != SS_READY);
> if (unlikely(needs_conn)) {
> if (sock->state == SS_LISTENING) {
>
--
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