Re: Fw: [Bug 46131] New: 32-bit read from uninitialized memory in __ip_select_ident since 3.6-rc2

On Mon, 2012-08-20 at 18:24 +0200, Eric Dumazet wrote:

On Mon, 2012-08-20 at 09:03 -0700, Stephen Hemminger wrote:

quoted

Begin forwarded message:

Date: Sat, 18 Aug 2012 09:49:45 +0000 (UTC)
From: bugzilla-daemon@bugzilla.kernel.org
To: shemminger@linux-foundation.org
Subject: [Bug 46131] New: 32-bit read from uninitialized memory in __ip_select_ident since 3.6-rc2


https://bugzilla.kernel.org/show_bug.cgi?id=46131

           Summary: 32-bit read from uninitialized memory in
                    __ip_select_ident since 3.6-rc2
           Product: Networking
           Version: 2.5
    Kernel Version: 3.6-rc2
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: IPV4
        AssignedTo: shemminger@linux-foundation.org
        ReportedBy: casteyde.christian@free.fr
        Regression: Yes


Slacware64 current
Intel Core i7
6GB RAM

Since 3.6-rc2 (this is a regression from 3.6-rc1), I get the following warning
when I ping a host:

WARNING: kmemcheck: Caught 32-bit read from uninitialized memory
(ffff8801c3f79460)
00000000030380ab00000000450000482881000080118ebbc0a8010bc0a8010d
 u u u u i i i i i i i i i i i i i i i i i i i i i i i i i i i i
 ^
Pid: 5836, comm: udev-acl.ck Not tainted 3.6.0-rc2 #3 Acer Aspire 7750G/JE70_HR
RIP: 0010:[<ffffffff81697ed2>]  [<ffffffff81697ed2>]
__ip_select_ident+0x22/0x120
RSP: 0000:ffff8801c7e035e0  EFLAGS: 00010282
RAX: ffff88018194ab00 RBX: ffff88018b454700 RCX: 0000000000000040
RDX: 0000000000000001 RSI: ffff8801c7e035ec RDI: ffff8801c3f79450
RBP: ffff8801c7e03620 R08: ffff8801c54a8238 R09: 0000000000000000
R10: ffff8801c7e03770 R11: 0000000000000050 R12: ffff8801c3f79450
R13: 0000000000000000 R14: ffff88018db74a80 R15: ffff8801c3f79450
FS:  00007f0692dfb740(0000) GS:ffff8801c7e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8801c6b06a88 CR3: 00000001a9ae5000 CR4: 00000000000407f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400
 [<ffffffff816a2aa8>] __ip_make_skb+0x2f8/0x3c0
 [<ffffffff816a2bd7>] ip_push_pending_frames+0x17/0x30
 [<ffffffff816d16be>] icmp_push_reply+0xee/0x120
 [<ffffffff816d1b95>] icmp_send+0x4a5/0xb10
 [<ffffffff816ce5b8>] __udp4_lib_rcv+0x568/0x920
 [<ffffffff816ce985>] udp_rcv+0x15/0x20
 [<ffffffff8169b0d7>] ip_local_deliver_finish+0x107/0x460
 [<ffffffff8169b6f8>] ip_local_deliver+0x88/0x90
 [<ffffffff8169ab10>] ip_rcv_finish+0x120/0x5e0
 [<ffffffff8169b919>] ip_rcv+0x219/0x2b0
 [<ffffffff8164de82>] __netif_receive_skb+0x742/0x9b0
 [<ffffffff8164ef68>] netif_receive_skb+0x28/0x1e0
 [<ffffffff817a2de5>] ieee80211_deliver_skb.isra.28+0xa5/0x220
 [<ffffffff817a3e87>] ieee80211_rx_handlers+0xf27/0x2380
 [<ffffffff817a55e7>] ieee80211_prepare_and_rx_handle+0x307/0x8b0
 [<ffffffff817a620e>] ieee80211_rx+0x67e/0xce0
 [<ffffffff814b819c>] ath_rx_tasklet+0xc9c/0x1350
 [<ffffffff814b6024>] ath9k_tasklet+0xe4/0x140
 [<ffffffff810784ec>] tasklet_action+0x6c/0xe0
 [<ffffffff81078e5a>] __do_softirq+0xba/0x180
 [<ffffffff817e32dc>] call_softirq+0x1c/0x30
 [<ffffffff8103a4ed>] do_softirq+0x7d/0xb0
 [<ffffffff81079276>] irq_exit+0x96/0xc0
 [<ffffffff81039f8e>] do_IRQ+0x5e/0xd0
 [<ffffffff817e18ac>] ret_from_intr+0x0/0x13
 [<ffffffffffffffff>] 0xffffffffffffffff

Thanks for the report, I am testing a patch.

Christian, are you sure its a 3.6.-rc2 regression, because I believe its
an old bug...

Could you test following fix ?

(ip_select_ident() must be called _after_ iph->daddr is set)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 147ccc3..c196d74 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c

@@ -1338,10 +1338,10 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
 	iph->ihl = 5;
 	iph->tos = inet->tos;
 	iph->frag_off = df;
-	ip_select_ident(iph, &rt->dst, sk);
 	iph->ttl = ttl;
 	iph->protocol = sk->sk_protocol;
 	ip_copy_addrs(iph, fl4);
+	ip_select_ident(iph, &rt->dst, sk);
 
 	if (opt) {
 		iph->ihl += opt->optlen>>2;