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BUG: KASAN: use-after-free in batadv_interface_tx+0xa24/0x1470 net/batman-adv/soft-interface.c:226
Read of size 2 at addr ffff88808ef4880b by task syz-executor4/31978

CPU: 1 PID: 31978 Comm: syz-executor4 Not tainted 5.0.0-rc5 #60
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+0x172/0x1f0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
 kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
 __asan_report_load_n_noabort+0xf/0x20 mm/kasan/generic_report.c:145
 batadv_interface_tx+0xa24/0x1470 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+0x346/0x640 net/core/dev.c:3930
 packet_direct_xmit+0xfb/0x170 net/packet/af_packet.c:246
 packet_snd net/packet/af_packet.c:2933 [inline]
 packet_sendmsg+0x3879/0x5ab0 net/packet/af_packet.c:2958
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg+0xdd/0x130 net/socket.c:631
 __sys_sendto+0x262/0x380 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+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457e39
Code: ad b8 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fe1ff421c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000457e39
RDX: 0000000000000044 RSI: 0000000020000240 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fe1ff4226d4
R13: 00000000004c548a R14: 00000000004d9260 R15: 00000000ffffffff

Allocated by task 3868:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc mm/kasan/common.c:496 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:469
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:504
 __do_kmalloc_node mm/slab.c:3673 [inline]
 __kmalloc_node+0x4e/0x70 mm/slab.c:3680
 kmalloc_node include/linux/slab.h:588 [inline]
 kvmalloc_node+0x68/0x100 mm/util.c:416
 kvmalloc include/linux/mm.h:604 [inline]
 seq_buf_alloc fs/seq_file.c:32 [inline]
 seq_read+0x832/0x1130 fs/seq_file.c:204
 kernfs_fop_read+0xed/0x560 fs/kernfs/file.c:252
 __vfs_read+0x116/0x8c0 fs/read_write.c:416
 vfs_read+0x194/0x3e0 fs/read_write.c:452
 ksys_read+0xea/0x1f0 fs/read_write.c:578
 __do_sys_read fs/read_write.c:588 [inline]
 __se_sys_read fs/read_write.c:586 [inline]
 __x64_sys_read+0x73/0xb0 fs/read_write.c:586
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 3868:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:458
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:466
 __cache_free mm/slab.c:3487 [inline]
 kfree+0xcf/0x230 mm/slab.c:3806
 kvfree+0x61/0x70 mm/util.c:445
 seq_release+0x54/0x80 fs/seq_file.c:359
 kernfs_fop_release+0xf7/0x1a0 fs/kernfs/file.c:781
 __fput+0x2df/0x8d0 fs/file_table.c:278
 ____fput+0x16/0x20 fs/file_table.c:309
 task_work_run+0x14a/0x1c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x273/0x2c0 arch/x86/entry/common.c:166
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808ef48400
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 1035 bytes inside of
 4096-byte region [ffff88808ef48400, ffff88808ef49400)
The buggy address belongs to the page:
page:ffffea00023bd200 count:1 mapcount:0 mapping:ffff88812c3f0dc0 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea00012e7f88 ffffea0001594788 ffff88812c3f0dc0
raw: 0000000000000000 ffff88808ef48400 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808ef48700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808ef48780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88808ef48800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff88808ef48880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808ef48900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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