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843d926b00
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Eric Dumazet 843d926b00 ipv6: avoid lockdep issue in fib6_del() 
syzbot reported twice a lockdep issue in fib6_del() [1]
which I think is caused by net->ipv6.fib6_null_entry
having a NULL fib6_table pointer.

fib6_del() already checks for fib6_null_entry special
case, we only need to return earlier.

Bug seems to occur very rarely, I have thus chosen
a 'bug origin' that makes backports not too complex.

[1]
WARNING: suspicious RCU usage
5.9.0-rc4-syzkaller #0 Not tainted
-----------------------------
net/ipv6/ip6_fib.c:1996 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
4 locks held by syz-executor.5/8095:
 #0: ffffffff8a7ea708 (rtnl_mutex){+.+.}-{3:3}, at: ppp_release+0x178/0x240 drivers/net/ppp/ppp_generic.c:401
 #1: ffff88804c422dd8 (&net->ipv6.fib6_gc_lock){+.-.}-{2:2}, at: spin_trylock_bh include/linux/spinlock.h:414 [inline]
 #1: ffff88804c422dd8 (&net->ipv6.fib6_gc_lock){+.-.}-{2:2}, at: fib6_run_gc+0x21b/0x2d0 net/ipv6/ip6_fib.c:2312
 #2: ffffffff89bd6a40 (rcu_read_lock){....}-{1:2}, at: __fib6_clean_all+0x0/0x290 net/ipv6/ip6_fib.c:2613
 #3: ffff8880a82e6430 (&tb->tb6_lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:359 [inline]
 #3: ffff8880a82e6430 (&tb->tb6_lock){+.-.}-{2:2}, at: __fib6_clean_all+0x107/0x290 net/ipv6/ip6_fib.c:2245

stack backtrace:
CPU: 1 PID: 8095 Comm: syz-executor.5 Not tainted 5.9.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 fib6_del+0x12b4/0x1630 net/ipv6/ip6_fib.c:1996
 fib6_clean_node+0x39b/0x570 net/ipv6/ip6_fib.c:2180
 fib6_walk_continue+0x4aa/0x8e0 net/ipv6/ip6_fib.c:2102
 fib6_walk+0x182/0x370 net/ipv6/ip6_fib.c:2150
 fib6_clean_tree+0xdb/0x120 net/ipv6/ip6_fib.c:2230
 __fib6_clean_all+0x120/0x290 net/ipv6/ip6_fib.c:2246
 fib6_clean_all net/ipv6/ip6_fib.c:2257 [inline]
 fib6_run_gc+0x113/0x2d0 net/ipv6/ip6_fib.c:2320
 ndisc_netdev_event+0x217/0x350 net/ipv6/ndisc.c:1805
 notifier_call_chain+0xb5/0x200 kernel/notifier.c:83
 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:2033
 call_netdevice_notifiers_extack net/core/dev.c:2045 [inline]
 call_netdevice_notifiers net/core/dev.c:2059 [inline]
 dev_close_many+0x30b/0x650 net/core/dev.c:1634
 rollback_registered_many+0x3a8/0x1210 net/core/dev.c:9261
 rollback_registered net/core/dev.c:9329 [inline]
 unregister_netdevice_queue+0x2dd/0x570 net/core/dev.c:10410
 unregister_netdevice include/linux/netdevice.h:2774 [inline]
 ppp_release+0x216/0x240 drivers/net/ppp/ppp_generic.c:403
 __fput+0x285/0x920 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:141
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:163 [inline]
 exit_to_user_mode_prepare+0x1e1/0x200 kernel/entry/common.c:190
 syscall_exit_to_user_mode+0x7e/0x2e0 kernel/entry/common.c:265
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 421842edea ("net/ipv6: Add fib6_null_entry")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: David Ahern <dsahern@gmail.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-09-08 19:56:25 -07:00
..
6lowpan
9p treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
802
8021q treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
appletalk appletalk: Fix atalk_proc_init() return path 2020-08-03 15:48:32 -07:00
atm treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
ax25 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-07-25 17:49:04 -07:00
batman-adv batman-adv: bla: use netif_rx_ni when not in interrupt context 2020-08-18 19:40:03 +02:00
bluetooth mm, treewide: rename kzfree() to kfree_sensitive() 2020-08-07 11:33:22 -07:00
bpf treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
bpfilter Merge branch 'exec-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-08-04 14:27:25 -07:00
bridge netfilter: ebtables: reject bogus getopt len value 2020-08-14 11:59:08 +02:00
caif net: caif: fix error code handling 2020-08-25 07:50:25 -07:00
can treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
ceph treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
core Revert "netns: don't disable BHs when locking "nsid_lock"" 2020-09-07 14:32:39 -07:00
dcb
dccp treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
decnet treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
dns_resolver
dsa net: dsa: link interfaces with the DSA master to get rid of lockdep warnings 2020-09-08 19:40:09 -07:00
ethernet
ethtool ethtool: Don't omit the netlink reply if no features were changed 2020-08-18 16:00:24 -07:00
hsr hsr: Use %pM format specifier for MAC addresses 2020-07-31 16:46:26 -07:00
ieee802154 treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
ife
ipv4 netfilter: delete repeated words 2020-08-28 20:11:38 +02:00
ipv6 ipv6: avoid lockdep issue in fib6_del() 2020-09-08 19:56:25 -07:00
iucv treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
kcm net: pass a sockptr_t into ->setsockopt 2020-07-24 15:41:54 -07:00
key Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-02 01:02:12 -07:00
l2tp l2tp: improve API documentation in l2tp_core.h 2020-07-30 16:45:31 -07:00
l3mdev net: Fix some comments 2020-08-27 07:55:59 -07:00
lapb
llc net: pass a sockptr_t into ->setsockopt 2020-07-24 15:41:54 -07:00
mac80211 mac80211: reduce packet loss event false positives 2020-08-27 10:53:20 +02:00
mac802154 mm, treewide: rename kzfree() to kfree_sensitive() 2020-08-07 11:33:22 -07:00
mpls treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
mptcp Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-09-03 18:50:48 -07:00
ncsi treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
netfilter Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-09-03 18:50:48 -07:00
netlabel netlabel: fix problems with mapping removal 2020-08-24 16:08:00 -07:00
netlink Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-09-03 18:50:48 -07:00
netrom treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
nfc net/nfc/rawsock.c: add CAP_NET_RAW check. 2020-08-11 10:34:30 -07:00
nsh
openvswitch treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
packet net/packet: fix overflow in tpacket_rcv 2020-09-04 11:56:02 -07:00
phonet treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
psample
qrtr net: qrtr: fix usage of idr in port assignment to socket 2020-08-17 15:00:41 -07:00
rds treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
rfkill
rose treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
rxrpc Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-09-03 18:50:48 -07:00
sched act_ife: load meta modules before tcf_idr_check_alloc() 2020-09-04 22:08:59 -07:00
sctp Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-09-03 18:50:48 -07:00
smc Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-09-03 18:50:48 -07:00
strparser
sunrpc Fixes: 2020-08-25 18:01:36 -07:00
switchdev net: switchdev: kerneldoc fixes 2020-07-13 17:20:40 -07:00
tipc Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-09-03 18:50:48 -07:00
tls net/tls: Fix kmap usage 2020-08-11 10:20:34 -07:00
unix treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
vmw_vsock vsock: fix potential null pointer dereference in vsock_poll() 2020-08-12 12:56:06 -07:00
wimax
wireless Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-09-03 18:50:48 -07:00
x25 treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
xdp xdp: Prevent kernel-infoleak in xsk_getsockopt() 2020-07-28 12:50:15 +02:00
xfrm treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
compat.c net/scm: Fix typo in SCM_RIGHTS compat refactoring 2020-08-07 12:43:25 -07:00
devres.c
Kconfig
Makefile
socket.c net: Fix some comments 2020-08-27 07:55:59 -07:00
sysctl_net.c