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Message-Id: <20191012011455.211242-1-maheshb@google.com>
Date: Fri, 11 Oct 2019 18:14:55 -0700
From: Mahesh Bandewar <maheshb@...gle.com>
To: Netdev <netdev@...r.kernel.org>
Cc: Eric Dumazet <edumazet@...gle.com>, Wei Wang <weiwan@...gle.com>,
David Miller <davem@...emloft.net>,
Mahesh Bandewar <mahesh@...dewar.net>,
Mahesh Bandewar <maheshb@...gle.com>
Subject: [PATCHv3 next] blackhole_netdev: fix syzkaller reported issue
While invalidating the dst, we assign backhole_netdev instead of
loopback device. However, this device does not have idev pointer
and hence no ip6_ptr even if IPv6 is enabled. Possibly this has
triggered the syzbot reported crash.
The syzbot report does not have reproducer, however, this is the
only device that doesn't have matching idev created.
Crash instruction is :
static inline bool ip6_ignore_linkdown(const struct net_device *dev)
{
const struct inet6_dev *idev = __in6_dev_get(dev);
return !!idev->cnf.ignore_routes_with_linkdown; <= crash
}
Also ipv6 always assumes presence of idev and never checks for it
being NULL (as does the above referenced code). So adding a idev
for the blackhole_netdev to avoid this class of crashes in the future.
---
syzbot has found the following crash on:
HEAD commit: 125b7e09 net: tc35815: Explicitly check NET_IP_ALIGN is no..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git master
console output: https://syzkaller-buganizer.googleplex.com/text?tag=CrashLog&id=96236769ac48d9c2eb3a0db5385370ea6940be83
kernel config: https://syzkaller-buganizer.googleplex.com/text?tag=Config&id=1ed331b637302a68174fdbe34315b781b7c7ab1e
dashboard link: https://syzkaller.appspot.com/bug?extid=86298614df433d7f3824
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
Unfortunately, I don't have any reproducer for this crash yet.
See http://go/syzbot for details on how to handle this bug.
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 16525 Comm: syz-executor.2 Not tainted 5.3.0-rc3+ #159
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:ip6_ignore_linkdown include/net/addrconf.h:402 [inline]
RIP: 0010:find_match+0x132/0xd70 net/ipv6/route.c:743
Code: 0f b6 75 b0 40 84 f6 0f 84 ad 01 00 00 e8 c6 4c 34 fb 49 8d bf 3c 02 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 15
RSP: 0018:ffff88806c037038 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff888094c5cd60 RCX: ffffc9000b791000
RDX: 0000000000000047 RSI: ffffffff863e3caa RDI: 000000000000023c
RBP: ffff88806c037098 R08: ffff888063de0600 R09: ffff88806c037288
R10: fffffbfff134af07 R11: ffffffff89a5783f R12: 0000000000000003
R13: ffff88806c037298 R14: ffff888094c5cd6f R15: 0000000000000000
FS: 00007fa15e7de700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000625208 CR3: 000000005e348000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__find_rr_leaf+0x14e/0x750 net/ipv6/route.c:831
find_rr_leaf net/ipv6/route.c:852 [inline]
rt6_select net/ipv6/route.c:896 [inline]
fib6_table_lookup+0x697/0xdb0 net/ipv6/route.c:2164
ip6_pol_route+0x1f6/0xaf0 net/ipv6/route.c:2200
ip6_pol_route_output+0x54/0x70 net/ipv6/route.c:2452
fib6_rule_lookup+0x133/0x7a0 net/ipv6/fib6_rules.c:113
ip6_route_output_flags_noref+0x2d6/0x360 net/ipv6/route.c:2484
ip6_route_output_flags+0x106/0x4d0 net/ipv6/route.c:2497
ip6_route_output include/net/ip6_route.h:98 [inline]
ip6_dst_lookup_tail+0x1042/0x1ef0 net/ipv6/ip6_output.c:1022
ip6_dst_lookup_flow+0xa8/0x220 net/ipv6/ip6_output.c:1150
ip6_sk_dst_lookup_flow net/ipv6/ip6_output.c:1188 [inline]
ip6_sk_dst_lookup_flow+0x62a/0xb90 net/ipv6/ip6_output.c:1178
udpv6_sendmsg+0x17ba/0x2990 net/ipv6/udp.c:1439
inet6_sendmsg+0x9e/0xe0 net/ipv6/af_inet6.c:576
sock_sendmsg_nosec net/socket.c:637 [inline]
sock_sendmsg+0xd7/0x130 net/socket.c:657
__sys_sendto+0x262/0x380 net/socket.c:1952
__do_sys_sendto net/socket.c:1964 [inline]
__se_sys_sendto net/socket.c:1960 [inline]
__x64_sys_sendto+0xe1/0x1a0 net/socket.c:1960
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fa15e7ddc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000459829
RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000007
RBP: 000000000075c1c0 R08: 0000000020001000 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa15e7de6d4
R13: 00000000004c77e7 R14: 00000000004dd048 R15: 00000000ffffffff
Modules linked in:
---[ end trace 4b3ce5eddd15c8f6 ]---
RIP: 0010:ip6_ignore_linkdown include/net/addrconf.h:402 [inline]
RIP: 0010:find_match+0x132/0xd70 net/ipv6/route.c:743
Code: 0f b6 75 b0 40 84 f6 0f 84 ad 01 00 00 e8 c6 4c 34 fb 49 8d bf 3c 02 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 15
RSP: 0018:ffff88806c037038 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff888094c5cd60 RCX: ffffc9000b791000
RDX: 0000000000000047 RSI: ffffffff863e3caa RDI: 000000000000023c
RBP: ffff88806c037098 R08: ffff888063de0600 R09: ffff88806c037288
R10: fffffbfff134af07 R11: ffffffff89a5783f R12: 0000000000000003
R13: ffff88806c037298 R14: ffff888094c5cd6f R15: 0000000000000000
FS: 00007fa15e7de700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000625208 CR3: 000000005e348000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Fixes: 8d7017fd621d ("blackhole_netdev: use blackhole_netdev to invalidate dst entries")
Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
CC: Eric Dumazet <edumazet@...gle.com>
CC: Wei Wang <weiwan@...gle.com>
---
v1->v2:
fixed missing update in ip6_dst_ifdown()
v2->v3:
added idev cleanup step in addrconf_cleanup()
net/ipv6/addrconf.c | 7 ++++++-
net/ipv6/route.c | 15 ++++++---------
2 files changed, 12 insertions(+), 10 deletions(-)
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 98d82305d6de..2a01404aba78 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -6995,7 +6995,7 @@ static struct rtnl_af_ops inet6_ops __read_mostly = {
int __init addrconf_init(void)
{
- struct inet6_dev *idev;
+ struct inet6_dev *idev, *bdev;
int i, err;
err = ipv6_addr_label_init();
@@ -7035,10 +7035,14 @@ int __init addrconf_init(void)
*/
rtnl_lock();
idev = ipv6_add_dev(init_net.loopback_dev);
+ bdev = ipv6_add_dev(blackhole_netdev);
rtnl_unlock();
if (IS_ERR(idev)) {
err = PTR_ERR(idev);
goto errlo;
+ } else if (IS_ERR(bdev)) {
+ err = PTR_ERR(bdev);
+ goto errlo;
}
ip6_route_init_special_entries();
@@ -7123,6 +7127,7 @@ void addrconf_cleanup(void)
addrconf_ifdown(dev, 1);
}
addrconf_ifdown(init_net.loopback_dev, 2);
+ addrconf_ifdown(blackhole_netdev, 2);
/*
* Check hash table.
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index a63ff85fe141..742120728869 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -155,10 +155,9 @@ void rt6_uncached_list_del(struct rt6_info *rt)
static void rt6_uncached_list_flush_dev(struct net *net, struct net_device *dev)
{
- struct net_device *loopback_dev = net->loopback_dev;
int cpu;
- if (dev == loopback_dev)
+ if (dev == net->loopback_dev)
return;
for_each_possible_cpu(cpu) {
@@ -171,7 +170,7 @@ static void rt6_uncached_list_flush_dev(struct net *net, struct net_device *dev)
struct net_device *rt_dev = rt->dst.dev;
if (rt_idev->dev == dev) {
- rt->rt6i_idev = in6_dev_get(loopback_dev);
+ rt->rt6i_idev = in6_dev_get(blackhole_netdev);
in6_dev_put(rt_idev);
}
@@ -386,13 +385,11 @@ static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
{
struct rt6_info *rt = (struct rt6_info *)dst;
struct inet6_dev *idev = rt->rt6i_idev;
- struct net_device *loopback_dev =
- dev_net(dev)->loopback_dev;
- if (idev && idev->dev != loopback_dev) {
- struct inet6_dev *loopback_idev = in6_dev_get(loopback_dev);
- if (loopback_idev) {
- rt->rt6i_idev = loopback_idev;
+ if (idev && idev->dev != dev_net(dev)->loopback_dev) {
+ struct inet6_dev *ibdev = in6_dev_get(blackhole_netdev);
+ if (ibdev) {
+ rt->rt6i_idev = ibdev;
in6_dev_put(idev);
}
}
--
2.23.0.700.g56cf767bdb-goog
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