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BUG: KASAN: use-after-free in tasklet_action+0x29f/0x340 kernel/softirq.c:506
Read of size 8 at addr ffff88809bc0ce90 by task kworker/u4:2/34

CPU: 1 PID: 34 Comm: kworker/u4:2 Not tainted 4.14.257-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bat_events batadv_nc_worker
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x281 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
 kasan_report_error.cold+0x8a/0x191 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_load8_noabort+0x68/0x70 mm/kasan/report.c:430
 tasklet_action+0x29f/0x340 kernel/softirq.c:506
 __do_softirq+0x24d/0x9ff kernel/softirq.c:288
 do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1016
 </IRQ>
 do_softirq.part.0+0x154/0x1b0 kernel/softirq.c:332
 do_softirq kernel/softirq.c:324 [inline]
 __local_bh_enable_ip+0x12b/0x170 kernel/softirq.c:185
 spin_unlock_bh include/linux/spinlock.h:362 [inline]
 batadv_nc_purge_paths+0x20c/0x300 net/batman-adv/network-coding.c:481
 batadv_nc_worker+0x628/0xc50 net/batman-adv/network-coding.c:729
 process_one_work+0x793/0x14a0 kernel/workqueue.c:2117
 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2251
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 12090:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x131/0x3d0 mm/slab.c:3618
 kmalloc include/linux/slab.h:488 [inline]
 kzalloc include/linux/slab.h:661 [inline]
 bcm_tx_setup net/can/bcm.c:960 [inline]
 bcm_sendmsg+0x20bb/0x3ae0 net/can/bcm.c:1396
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb5/0x100 net/socket.c:656
 ___sys_sendmsg+0x6c8/0x800 net/socket.c:2062
 __sys_sendmsg+0xa3/0x120 net/socket.c:2096
 SYSC_sendmsg net/socket.c:2107 [inline]
 SyS_sendmsg+0x27/0x40 net/socket.c:2103
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 12085:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xc9/0x250 mm/slab.c:3815
 bcm_release+0x255/0x900 net/can/bcm.c:1571
 __sock_release+0xcd/0x2b0 net/socket.c:602
 sock_close+0x15/0x20 net/socket.c:1139
 __fput+0x25f/0x7a0 fs/file_table.c:210
 task_work_run+0x11f/0x190 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

The buggy address belongs to the object at ffff88809bc0cdc0
 which belongs to the cache kmalloc-1024 of size 1024
The buggy address is located 208 bytes inside of
 1024-byte region [ffff88809bc0cdc0, ffff88809bc0d1c0)
The buggy address belongs to the page:
page:ffffea00026f0300 count:1 mapcount:0 mapping:ffff88809bc0c040 index:0xffff88809bc0c040 compound_mapcount: 0
flags: 0xfff00000008100(slab|head)
raw: 00fff00000008100 ffff88809bc0c040 ffff88809bc0c040 0000000100000002
raw: ffffea00026e41a0 ffffea00026d79a0 ffff88813fe74ac0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809bc0cd80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff88809bc0ce00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88809bc0ce80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff88809bc0cf00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809bc0cf80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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