general protection fault in nexthop_is_blackhole

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c3d8f220 Merge tag 'kbuild-fixes-v5.9' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11c48c96900000
kernel config: https://syzkaller.appspot.com/x/.config?x=bb68b9e8a8cc842f
dashboard link: https://syzkaller.appspot.com/bug?extid=b2c08a2f5cfef635cc3a
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14d75e39900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12aea519900000

The issue was bisected to:

commit de47c5d8e11dda678e4354eeb4235e58e92f7cd2
Author: Hariprasad Kelam <haripras...@gmail.com>
Date: Sat Jun 8 09:00:50 2019 +0000

af_key: make use of BUG_ON macro

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10450972900000
final oops: https://syzkaller.appspot.com/x/report.txt?x=12450972900000
console output: https://syzkaller.appspot.com/x/log.txt?x=14450972900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b2c08a...@syzkaller.appspotmail.com
Fixes: de47c5d8e11d ("af_key: make use of BUG_ON macro")

IPv6: RTM_NEWROUTE with no NLM_F_CREATE or NLM_F_REPLACE
IPv6: NLM_F_CREATE should be set when creating new route
IPv6: NLM_F_CREATE should be set when creating new route
general protection fault, probably for non-canonical address 0xdffffc0000000010: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000080-0x0000000000000087]
CPU: 0 PID: 7050 Comm: syz-executor320 Not tainted 5.9.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:nexthop_is_blackhole+0x145/0x250 include/net/nexthop.h:240
Code: 4d fa 49 83 c6 10 4c 89 f0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 f7 e8 39 f0 8c fa 49 8b 1e 48 83 eb 80 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 1c f0 8c fa 48 8b 1b e8 e4 4e 02
RSP: 0018:ffffc900061172b8 EFLAGS: 00010202
RAX: 0000000000000010 RBX: 0000000000000080 RCX: ffff888091444300
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffffffff8727dfc7 R09: ffffed1012299e09
R10: ffffed1012299e09 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880919da280 R14: ffff8880a9576610 R15: dffffc0000000000
FS: 0000000001a89880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000300 CR3: 00000000a7555000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
rt6_fill_node+0xfe9/0x1f90 net/ipv6/route.c:5584
inet6_rt_notify+0x2ab/0x500 net/ipv6/route.c:6017
fib6_add_rt2node net/ipv6/ip6_fib.c:1246 [inline]
fib6_add+0x203b/0x3bd0 net/ipv6/ip6_fib.c:1473
__ip6_ins_rt net/ipv6/route.c:1317 [inline]
ip6_route_add+0x84/0x120 net/ipv6/route.c:3744
inet6_rtm_newroute+0x22f/0x2150 net/ipv6/route.c:5360
rtnetlink_rcv_msg+0x889/0xd40 net/core/rtnetlink.c:5563
netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2470
netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1330
netlink_sendmsg+0xa57/0xd70 net/netlink/af_netlink.c:1919
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg net/socket.c:671 [inline]
____sys_sendmsg+0x519/0x800 net/socket.c:2353
___sys_sendmsg net/socket.c:2407 [inline]
__sys_sendmsg+0x2b1/0x360 net/socket.c:2440
do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x443ef9
Code: e8 8c 07 03 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 bb 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd64ccd428 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000443ef9
RDX: 0000000000000000 RSI: 0000000020000300 RDI: 0000000000000003
RBP: 00007ffd64ccd430 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000b6f1
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace e62dc7d3de715e59 ]---
RIP: 0010:nexthop_is_blackhole+0x145/0x250 include/net/nexthop.h:240
Code: 4d fa 49 83 c6 10 4c 89 f0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 f7 e8 39 f0 8c fa 49 8b 1e 48 83 eb 80 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 1c f0 8c fa 48 8b 1b e8 e4 4e 02
RSP: 0018:ffffc900061172b8 EFLAGS: 00010202
RAX: 0000000000000010 RBX: 0000000000000080 RCX: ffff888091444300
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffffffff8727dfc7 R09: ffffed1012299e09
R10: ffffed1012299e09 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880919da280 R14: ffff8880a9576610 R15: dffffc0000000000
FS: 0000000001a89880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000300 CR3: 00000000a7555000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+b2c08a...@syzkaller.appspotmail.com

Tested on:

commit: 15bc20c6 Merge tag 'tty-5.9-rc3' of git://git.kernel.org/p..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=891ca5711a9f1650

dashboard link: https://syzkaller.appspot.com/bug?extid=b2c08a2f5cfef635cc3a
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

Note: testing is done by a robot and is best-effort only.

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+b2c08a...@syzkaller.appspotmail.com

Tested on:

commit: 9c7d619b Merge tag 'perf-tools-fixes-for-v5.9-2020-09-01' ..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
kernel config: https://syzkaller.appspot.com/x/.config?x=e1c560d0f4e121c9

[Anant Thazhemadam]

Hi,

This bug doesn't seem to be getting triggered anymore for the appropriate kernel(s). 
Could someone please point out the fix that might've been merged, so we can close 
this as well?

Thanks,

Anant 

[Dmitry Vyukov]

Hi Anant,

You need to send this to kernel lists/maintainers. Nobody useful is
reading syzkaller-bugs mailing list.

[Anant Thazhemadam]

Noted. Thank you.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit eeaac3634ee0e3f35548be35275efeca888e9b23
Author: Nikolay Aleksandrov <nik...@cumulusnetworks.com>
Date: Sat Aug 22 12:06:36 2020 +0000

net: nexthop: don't allow empty NHA_GROUP

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=116177a7900000
start commit: c3d8f220 Merge tag 'kbuild-fixes-v5.9' of git://git.kernel..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=bb68b9e8a8cc842f
dashboard link: https://syzkaller.appspot.com/bug?extid=b2c08a2f5cfef635cc3a

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14d75e39900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12aea519900000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: net: nexthop: don't allow empty NHA_GROUP

[Dmitry Vyukov]