[syzbot] [net?] KASAN: null-ptr-deref Read in __fl_put

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5b7c4cabbb65 Merge tag 'net-next-6.3' of git://git.kernel...
git tree: net
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10874f28c80000
kernel config: https://syzkaller.appspot.com/x/.config?x=c74c134cc415a89b
dashboard link: https://syzkaller.appspot.com/bug?extid=baabf3efa7c1e57d28b2
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=166c5e50c80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1094ca50c80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b3d83e162bd2/disk-5b7c4cab.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ad7e8c0fc7b5/vmlinux-5b7c4cab.xz
kernel image: https://storage.googleapis.com/syzbot-assets/060fac08a8fd/bzImage-5b7c4cab.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+baabf3...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:72 [inline]
BUG: KASAN: null-ptr-deref in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
BUG: KASAN: null-ptr-deref in refcount_read include/linux/refcount.h:147 [inline]
BUG: KASAN: null-ptr-deref in __refcount_add_not_zero include/linux/refcount.h:152 [inline]
BUG: KASAN: null-ptr-deref in __refcount_inc_not_zero include/linux/refcount.h:227 [inline]
BUG: KASAN: null-ptr-deref in refcount_inc_not_zero include/linux/refcount.h:245 [inline]
BUG: KASAN: null-ptr-deref in maybe_get_net include/net/net_namespace.h:269 [inline]
BUG: KASAN: null-ptr-deref in tcf_exts_get_net include/net/pkt_cls.h:260 [inline]
BUG: KASAN: null-ptr-deref in __fl_put net/sched/cls_flower.c:513 [inline]
BUG: KASAN: null-ptr-deref in __fl_put+0x13e/0x3b0 net/sched/cls_flower.c:508
Read of size 4 at addr 000000000000014c by task syz-executor548/5082

CPU: 0 PID: 5082 Comm: syz-executor548 Not tainted 6.2.0-syzkaller-05251-g5b7c4cabbb65 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
print_report mm/kasan/report.c:420 [inline]
kasan_report+0xec/0x130 mm/kasan/report.c:517
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x141/0x190 mm/kasan/generic.c:189
instrument_atomic_read include/linux/instrumented.h:72 [inline]
atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
refcount_read include/linux/refcount.h:147 [inline]
__refcount_add_not_zero include/linux/refcount.h:152 [inline]
__refcount_inc_not_zero include/linux/refcount.h:227 [inline]
refcount_inc_not_zero include/linux/refcount.h:245 [inline]
maybe_get_net include/net/net_namespace.h:269 [inline]
tcf_exts_get_net include/net/pkt_cls.h:260 [inline]
__fl_put net/sched/cls_flower.c:513 [inline]
__fl_put+0x13e/0x3b0 net/sched/cls_flower.c:508
fl_change+0x101b/0x4ab0 net/sched/cls_flower.c:2341
tc_new_tfilter+0x97c/0x2290 net/sched/cls_api.c:2310
rtnetlink_rcv_msg+0x996/0xd50 net/core/rtnetlink.c:6165
netlink_rcv_skb+0x165/0x440 net/netlink/af_netlink.c:2574
netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
netlink_unicast+0x547/0x7f0 net/netlink/af_netlink.c:1365
netlink_sendmsg+0x925/0xe30 net/netlink/af_netlink.c:1942
sock_sendmsg_nosec net/socket.c:722 [inline]
sock_sendmsg+0xde/0x190 net/socket.c:745
____sys_sendmsg+0x334/0x900 net/socket.c:2504
___sys_sendmsg+0x110/0x1b0 net/socket.c:2558
__sys_sendmmsg+0x18f/0x460 net/socket.c:2644
__do_sys_sendmmsg net/socket.c:2673 [inline]
__se_sys_sendmmsg net/socket.c:2670 [inline]
__x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2670
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f3613969d19
Code: 28 c3 e8 1a 15 00 00 66 2e 0f 1f 84 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc884e0c88 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f36139d7ed0 RCX: 00007f3613969d19
RDX: 04924924924926d3 RSI: 0000000020000200 RDI: 0000000000000004
RBP: 00007ffc884e0c98 R08: 00007f36139d7e40 R09: 00007f36139d7e40
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc884e0ca0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
==================================================================


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