Re: [syzbot] [netfilter?] KASAN: slab-use-after-free Read in ip_skb_dst_mtu

[syzbot <syzbot+e5167d7144a62715044c@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: null-ptr-deref Write in ipvlan_process_v4_outbound

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: null-ptr-deref in atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline]
BUG: KASAN: null-ptr-deref in __refcount_add include/linux/refcount.h:182 [inline]
BUG: KASAN: null-ptr-deref in __refcount_inc include/linux/refcount.h:239 [inline]
BUG: KASAN: null-ptr-deref in refcount_inc include/linux/refcount.h:256 [inline]
BUG: KASAN: null-ptr-deref in ipvlan_process_v4_outbound+0x3f6/0x7b0 drivers/net/ipvlan/ipvlan_core.c:444
Write of size 4 at addr 0000000000000274 by task syz-executor.0/5580

CPU: 0 PID: 5580 Comm: syz-executor.0 Not tainted 6.8.0-rc7-syzkaller-g3aaa8ce7a335-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
 print_report+0xe6/0x540 mm/kasan/report.c:491
 kasan_report+0x142/0x180 mm/kasan/report.c:601
 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline]
 __refcount_add include/linux/refcount.h:182 [inline]
 __refcount_inc include/linux/refcount.h:239 [inline]
 refcount_inc include/linux/refcount.h:256 [inline]
 ipvlan_process_v4_outbound+0x3f6/0x7b0 drivers/net/ipvlan/ipvlan_core.c:444
 ipvlan_process_outbound drivers/net/ipvlan/ipvlan_core.c:544 [inline]
 ipvlan_xmit_mode_l3 drivers/net/ipvlan/ipvlan_core.c:606 [inline]
 ipvlan_queue_xmit+0xaa2/0x11f0 drivers/net/ipvlan/ipvlan_core.c:672
 ipvlan_start_xmit+0x4a/0x150 drivers/net/ipvlan/ipvlan_main.c:222
 __netdev_start_xmit include/linux/netdevice.h:4986 [inline]
 netdev_start_xmit include/linux/netdevice.h:5000 [inline]
 xmit_one net/core/dev.c:3547 [inline]
 dev_hard_start_xmit+0x242/0x770 net/core/dev.c:3563
 sch_direct_xmit+0x2b6/0x5f0 net/sched/sch_generic.c:342
 qdisc_restart net/sched/sch_generic.c:407 [inline]
 __qdisc_run+0xbed/0x2150 net/sched/sch_generic.c:415
 __dev_xmit_skb net/core/dev.c:3839 [inline]
 __dev_queue_xmit+0xfc6/0x3b10 net/core/dev.c:4317
 packet_snd net/packet/af_packet.c:3081 [inline]
 packet_sendmsg+0x47f4/0x6240 net/packet/af_packet.c:3113
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:745
 __sys_sendto+0x3a4/0x4f0 net/socket.c:2191
 __do_sys_sendto net/socket.c:2203 [inline]
 __se_sys_sendto net/socket.c:2199 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2199
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77
RIP: 0033:0x7f5d1287dda9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5d136b40c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f5d129abf80 RCX: 00007f5d1287dda9
RDX: 0000000000005c13 RSI: 0000000020000280 RDI: 0000000000000003
RBP: 00007f5d128ca47a R08: 0000000000000000 R09: 000000000000002f
R10: 0000000000000806 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f5d129abf80 R15: 00007fffdca46778
 </TASK>
==================================================================


Tested on:

commit:         3aaa8ce7 Merge tag 'mm-hotfixes-stable-2024-03-07-16-1..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=12503a49180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=165e1d0fff4d3c47
dashboard link: https://syzkaller.appspot.com/bug?extid=e5167d7144a62715044c
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=154b4001180000