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Message-Id: <1460089718-25788-1-git-send-email-roopa@cumulusnetworks.com>
Date: Thu, 7 Apr 2016 21:28:38 -0700
From: Roopa Prabhu <roopa@...ulusnetworks.com>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org
Subject: [PATCH net] mpls: find_outdev: check for err ptr in addition to NULL check
From: Roopa Prabhu <roopa@...ulusnetworks.com>
find_outdev calls inet{,6}_fib_lookup_dev() or dev_get_by_index() to
find the output device. In case of an error, inet{,6}_fib_lookup_dev()
returns error pointer and dev_get_by_index() returns NULL. But the function
only checks for NULL and thus can end up calling dev_put on an ERR_PTR.
This patch adds an additional check for err ptr after the NULL check.
Before: Trying to add an mpls route with no oif from user, no available
path to 10.1.1.8 and no default route:
$ip -f mpls route add 100 as 200 via inet 10.1.1.8
[ 822.337195] BUG: unable to handle kernel NULL pointer dereference at
00000000000003a3
[ 822.340033] IP: [<ffffffff8148781e>] mpls_nh_assign_dev+0x10b/0x182
[ 822.340033] PGD 1db38067 PUD 1de9e067 PMD 0
[ 822.340033] Oops: 0000 [#1] SMP
[ 822.340033] Modules linked in:
[ 822.340033] CPU: 0 PID: 11148 Comm: ip Not tainted 4.5.0-rc7+ #54
[ 822.340033] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.7.5.1-0-g8936dbb-20141113_115728-nilsson.home.kraxel.org
04/01/2014
[ 822.340033] task: ffff88001db82580 ti: ffff88001dad4000 task.ti:
ffff88001dad4000
[ 822.340033] RIP: 0010:[<ffffffff8148781e>] [<ffffffff8148781e>]
mpls_nh_assign_dev+0x10b/0x182
[ 822.340033] RSP: 0018:ffff88001dad7a88 EFLAGS: 00010282
[ 822.340033] RAX: ffffffffffffff9b RBX: ffffffffffffff9b RCX:
0000000000000002
[ 822.340033] RDX: 00000000ffffff9b RSI: 0000000000000008 RDI:
0000000000000000
[ 822.340033] RBP: ffff88001ddc9ea0 R08: ffff88001e9f1768 R09:
0000000000000000
[ 822.340033] R10: ffff88001d9c1100 R11: ffff88001e3c89f0 R12:
ffffffff8187e0c0
[ 822.340033] R13: ffffffff8187e0c0 R14: ffff88001ddc9e80 R15:
0000000000000004
[ 822.340033] FS: 00007ff9ed798700(0000) GS:ffff88001fc00000(0000)
knlGS:0000000000000000
[ 822.340033] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 822.340033] CR2: 00000000000003a3 CR3: 000000001de89000 CR4:
00000000000006f0
[ 822.340033] Stack:
[ 822.340033] 0000000000000000 0000000100000000 0000000000000000
0000000000000000
[ 822.340033] 0000000000000000 0801010a00000000 0000000000000000
0000000000000000
[ 822.340033] 0000000000000004 ffffffff8148749b ffffffff8187e0c0
000000000000001c
[ 822.340033] Call Trace:
[ 822.340033] [<ffffffff8148749b>] ? mpls_rt_alloc+0x2b/0x3e
[ 822.340033] [<ffffffff81488e66>] ? mpls_rtm_newroute+0x358/0x3e2
[ 822.340033] [<ffffffff810e7bbc>] ? get_page+0x5/0xa
[ 822.340033] [<ffffffff813b7d94>] ? rtnetlink_rcv_msg+0x17e/0x191
[ 822.340033] [<ffffffff8111794e>] ? __kmalloc_track_caller+0x8c/0x9e
[ 822.340033] [<ffffffff813c9393>] ?
rht_key_hashfn.isra.20.constprop.57+0x14/0x1f
[ 822.340033] [<ffffffff813b7c16>] ? __rtnl_unlock+0xc/0xc
[ 822.340033] [<ffffffff813cb794>] ? netlink_rcv_skb+0x36/0x82
[ 822.340033] [<ffffffff813b4507>] ? rtnetlink_rcv+0x1f/0x28
[ 822.340033] [<ffffffff813cb2b1>] ? netlink_unicast+0x106/0x189
[ 822.340033] [<ffffffff813cb5b3>] ? netlink_sendmsg+0x27f/0x2c8
[ 822.340033] [<ffffffff81392ede>] ? sock_sendmsg_nosec+0x10/0x1b
[ 822.340033] [<ffffffff81393df1>] ? ___sys_sendmsg+0x182/0x1e3
[ 822.340033] [<ffffffff810e4f35>] ?
__alloc_pages_nodemask+0x11c/0x1e4
[ 822.340033] [<ffffffff8110619c>] ? PageAnon+0x5/0xd
[ 822.340033] [<ffffffff811062fe>] ? __page_set_anon_rmap+0x45/0x52
[ 822.340033] [<ffffffff810e7bbc>] ? get_page+0x5/0xa
[ 822.340033] [<ffffffff810e85ab>] ? __lru_cache_add+0x1a/0x3a
[ 822.340033] [<ffffffff81087ea9>] ? current_kernel_time64+0x9/0x30
[ 822.340033] [<ffffffff813940c4>] ? __sys_sendmsg+0x3c/0x5a
[ 822.340033] [<ffffffff8148f597>] ?
entry_SYSCALL_64_fastpath+0x12/0x6a
[ 822.340033] Code: 83 08 04 00 00 65 ff 00 48 8b 3c 24 e8 40 7c f2 ff
eb 13 48 c7 c3 9f ff ff ff eb 0f 89 ce e8 f1 ae f1 ff 48 89 c3 48 85 db
74 15 <48> 8b 83 08 04 00 00 65 ff 08 48 81 fb 00 f0 ff ff 76 0d eb 07
[ 822.340033] RIP [<ffffffff8148781e>] mpls_nh_assign_dev+0x10b/0x182
[ 822.340033] RSP <ffff88001dad7a88>
[ 822.340033] CR2: 00000000000003a3
[ 822.435363] ---[ end trace 98cc65e6f6b8bf11 ]---
After patch:
$ip -f mpls route add 100 as 200 via inet 10.1.1.8
RTNETLINK answers: Network is unreachable
Signed-off-by: Roopa Prabhu <roopa@...ulusnetworks.com>
Reported-by: David Miller <davem@...emloft.net>
---
I completely missed this during negative testing of my original
submission because of a default route always present. It was always
picking the default device in the failure case and no crash. This time
tested with no default route.
Thanks for catching it.
net/mpls/af_mpls.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index b18c5ed..0b80a71 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -543,6 +543,9 @@ static struct net_device *find_outdev(struct net *net,
if (!dev)
return ERR_PTR(-ENODEV);
+ if (IS_ERR(dev))
+ return dev;
+
/* The caller is holding rtnl anyways, so release the dev reference */
dev_put(dev);
--
1.9.1
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