general protection fault in ip_set_comment_free

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    d5d359b0 Merge branch 'for-linus' of git://git.kernel.org/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1366c611e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=cf8e288883e40aba
dashboard link: https://syzkaller.appspot.com/bug?extid=6a86565c74ebe30aea18
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12df0376e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14d225c9e00000

The bug was bisected to:

commit 23c42a403a9cfdbad6004a556c927be7dd61a8ee
Author: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>
Date:   Sat Oct 27 13:07:40 2018 +0000

    netfilter: ipset: Introduction of new commands and protocol version 7

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12508376e00000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=11508376e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=16508376e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6a86565c74ebe30aea18@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 23c42a403a9c ("netfilter: ipset: Introduction of new commands and protocol version 7")

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9800 Comm: syz-executor125 Not tainted 5.5.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:strlen+0x1f/0xa0 lib/string.c:527
Code: 00 66 2e 0f 1f 84 00 00 00 00 00 48 b8 00 00 00 00 00 fc ff df 55 48 89 fa 48 89 e5 48 c1 ea 03 41 54 49 89 fc 53 48 83 ec 08 <0f> b6 04 02 48 89 fa 83 e2 07 38 d0 7f 04 84 c0 75 4d 41 80 3c 24
RSP: 0018:ffffc90001fa6e90 EFLAGS: 00010286
RAX: dffffc0000000000 RBX: ffff88808f875f18 RCX: 1ffffffff14f6ffe
RDX: 0000000000000042 RSI: ffffffff8673d9a1 RDI: 0000000000000214
RBP: ffffc90001fa6ea8 R08: ffff8880870de500 R09: ffffed1011f0ebe3
R10: ffffed1011f0ebe2 R11: ffff88808f875f17 R12: 0000000000000214
R13: 0000000000000204 R14: ffff8880a5508200 R15: ffff88808f875f00
FS:  00000000014a2880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 00000000a9778000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 strlen include/linux/string.h:302 [inline]
 ip_set_comment_free+0x69/0xe0 net/netfilter/ipset/ip_set_core.c:402
 ip_set_ext_destroy include/linux/netfilter/ipset/ip_set.h:275 [inline]
 ip_set_ext_destroy include/linux/netfilter/ipset/ip_set.h:267 [inline]
 hash_net4_add+0x1b9a/0x2200 net/netfilter/ipset/ip_set_hash_gen.h:766
 hash_net4_uadt+0x596/0x940 net/netfilter/ipset/ip_set_hash_net.c:195
 call_ad+0x1a0/0x5a0 net/netfilter/ipset/ip_set_core.c:1716
 ip_set_ad.isra.0+0x572/0xb20 net/netfilter/ipset/ip_set_core.c:1804
 ip_set_uadd+0x37/0x50 net/netfilter/ipset/ip_set_core.c:1829
 nfnetlink_rcv_msg+0xcf2/0xfb0 net/netfilter/nfnetlink.c:229
 netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477
 nfnetlink_rcv+0x1ba/0x460 net/netfilter/nfnetlink.c:563
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0x58c/0x7d0 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0x91c/0xea0 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:639 [inline]
 sock_sendmsg+0xd7/0x130 net/socket.c:659
 ____sys_sendmsg+0x753/0x880 net/socket.c:2330
 ___sys_sendmsg+0x100/0x170 net/socket.c:2384
 __sys_sendmsg+0x105/0x1d0 net/socket.c:2417
 __do_sys_sendmsg net/socket.c:2426 [inline]
 __se_sys_sendmsg net/socket.c:2424 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2424
 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440379
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffcfb990398 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440379
RDX: 0000000000000000 RSI: 0000000020000d00 RDI: 0000000000000004
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000246 R12: 0000000000401c00
R13: 0000000000401c90 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace a6760a9ec122842d ]---
RIP: 0010:strlen+0x1f/0xa0 lib/string.c:527
Code: 00 66 2e 0f 1f 84 00 00 00 00 00 48 b8 00 00 00 00 00 fc ff df 55 48 89 fa 48 89 e5 48 c1 ea 03 41 54 49 89 fc 53 48 83 ec 08 <0f> b6 04 02 48 89 fa 83 e2 07 38 d0 7f 04 84 c0 75 4d 41 80 3c 24
RSP: 0018:ffffc90001fa6e90 EFLAGS: 00010286
RAX: dffffc0000000000 RBX: ffff88808f875f18 RCX: 1ffffffff14f6ffe
RDX: 0000000000000042 RSI: ffffffff8673d9a1 RDI: 0000000000000214
RBP: ffffc90001fa6ea8 R08: ffff8880870de500 R09: ffffed1011f0ebe3
R10: ffffed1011f0ebe2 R11: ffff88808f875f17 R12: 0000000000000214
R13: 0000000000000204 R14: ffff8880a5508200 R15: ffff88808f875f00
FS:  00000000014a2880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 00000000a9778000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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