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BUG: KASAN: use-after-free in batadv_interface_tx+0x160a/0x18b0 net/batman-adv/soft-interface.c:226
Read of size 2 at addr ffff8880943f184b by task syz-executor2/20524

CPU: 0 PID: 20524 Comm: syz-executor2 Not tainted 4.20.0-rc7+ #361
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+0x1d3/0x2c6 lib/dump_stack.c:113
 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
 __asan_report_load_n_noabort+0xf/0x20 mm/kasan/report.c:443
 batadv_interface_tx+0x160a/0x18b0 net/batman-adv/soft-interface.c:226
 __netdev_start_xmit include/linux/netdevice.h:4382 [inline]
 netdev_start_xmit include/linux/netdevice.h:4391 [inline]
 dev_direct_xmit+0x36c/0x6a0 net/core/dev.c:3930
 packet_direct_xmit+0xfb/0x170 net/packet/af_packet.c:246
 packet_snd net/packet/af_packet.c:2932 [inline]
 packet_sendmsg+0x298a/0x6ad0 net/packet/af_packet.c:2957
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:631
 __sys_sendto+0x3d7/0x670 net/socket.c:1788
 __do_sys_sendto net/socket.c:1800 [inline]
 __se_sys_sendto net/socket.c:1796 [inline]
 __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1796
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4579b9
Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffadbfcac78 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00000000004579b9
RDX: 000000000000000e RSI: 0000000020000180 RDI: 0000000000000004
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffadbfcb6d4
R13: 00000000004c4e37 R14: 00000000004d8640 R15: 00000000ffffffff

Allocated by task 23835:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc+0x12e/0x730 mm/slab.c:3554
 getname_flags+0xd0/0x590 fs/namei.c:140
 getname fs/namei.c:211 [inline]
 do_symlinkat+0x8b/0x2d0 fs/namei.c:4143
 __do_sys_symlink fs/namei.c:4173 [inline]
 __se_sys_symlink fs/namei.c:4171 [inline]
 __x64_sys_symlink+0x59/0x80 fs/namei.c:4171
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 23835:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kmem_cache_free+0x83/0x290 mm/slab.c:3760
 putname+0xf2/0x130 fs/namei.c:261
 do_symlinkat+0x18c/0x2d0 fs/namei.c:4161
 __do_sys_symlink fs/namei.c:4173 [inline]
 __se_sys_symlink fs/namei.c:4171 [inline]
 __x64_sys_symlink+0x59/0x80 fs/namei.c:4171
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880943f0a80
 which belongs to the cache names_cache of size 4096
The buggy address is located 3531 bytes inside of
 4096-byte region [ffff8880943f0a80, ffff8880943f1a80)
The buggy address belongs to the page:
page:ffffea000250fc00 count:1 mapcount:0 mapping:ffff88812c2bbc40 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea0002955d88 ffffea0002642808 ffff88812c2bbc40
raw: 0000000000000000 ffff8880943f0a80 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880943f1700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880943f1780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880943f1800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff8880943f1880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880943f1900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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