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BUG: KASAN: slab-out-of-bounds in atomic_sub_return include/asm-generic/atomic-instrumented.h:159 [inline]
BUG: KASAN: slab-out-of-bounds in skb_release_data+0x11d/0x7a0 net/core/skbuff.c:566
Write of size 4 at addr ffff88808c2a7e20 by task syz-executor.1/8634

CPU: 0 PID: 8634 Comm: syz-executor.1 Not tainted 5.1.0-rc2-next-20190327 #12
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
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x123/0x190 mm/kasan/generic.c:191
 kasan_check_write+0x14/0x20 mm/kasan/common.c:108
 atomic_sub_return include/asm-generic/atomic-instrumented.h:159 [inline]
 skb_release_data+0x11d/0x7a0 net/core/skbuff.c:566
 skb_release_all+0x4d/0x60 net/core/skbuff.c:631
 __kfree_skb net/core/skbuff.c:645 [inline]
 kfree_skb net/core/skbuff.c:663 [inline]
 kfree_skb+0xe8/0x390 net/core/skbuff.c:657
 skb_queue_purge+0x19/0x40 net/core/skbuff.c:2906
 packet_release+0x8eb/0xbf0 net/packet/af_packet.c:3026
 __sock_release+0xd3/0x2b0 net/socket.c:599
 sock_close+0x1b/0x30 net/socket.c:1247
 __fput+0x2e5/0x8d0 fs/file_table.c:278
 ____fput+0x16/0x20 fs/file_table.c:309
 task_work_run+0x14a/0x1c0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x90a/0x2fa0 kernel/exit.c:876
 do_group_exit+0x135/0x370 kernel/exit.c:980
 get_signal+0x399/0x1d50 kernel/signal.c:2577
 do_signal+0x87/0x1940 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
 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
RIP: 0033:0x458209
Code: Bad RIP value.
RSP: 002b:00007f90be60ccf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000073bf08 RCX: 0000000000458209
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000073bf08
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000073bf0c
R13: 00007ffc7f44273f R14: 00007f90be60d9c0 R15: 000000000073bf0c

Allocated by task 8017:
 save_stack+0x45/0xd0 mm/kasan/common.c:75
 set_track mm/kasan/common.c:87 [inline]
 __kasan_kmalloc mm/kasan/common.c:497 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:470
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:505
 slab_post_alloc_hook mm/slab.h:436 [inline]
 slab_alloc_node mm/slab.c:3335 [inline]
 kmem_cache_alloc_node+0x131/0x710 mm/slab.c:3645
 alloc_task_struct_node kernel/fork.c:157 [inline]
 dup_task_struct kernel/fork.c:844 [inline]
 copy_process.part.0+0x1d35/0x79d0 kernel/fork.c:1753
 copy_process kernel/fork.c:1710 [inline]
 _do_fork+0x257/0xfd0 kernel/fork.c:2227
 __do_sys_clone kernel/fork.c:2334 [inline]
 __se_sys_clone kernel/fork.c:2328 [inline]
 __x64_sys_clone+0xbf/0x150 kernel/fork.c:2328
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8017:
 save_stack+0x45/0xd0 mm/kasan/common.c:75
 set_track mm/kasan/common.c:87 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:459
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:467
 __cache_free mm/slab.c:3498 [inline]
 kmem_cache_free+0x86/0x260 mm/slab.c:3764
 free_task_struct kernel/fork.c:162 [inline]
 free_task+0xdd/0x120 kernel/fork.c:457
 copy_process.part.0+0x1a67/0x79d0 kernel/fork.c:2159
 copy_process kernel/fork.c:1710 [inline]
 _do_fork+0x257/0xfd0 kernel/fork.c:2227
 __do_sys_clone kernel/fork.c:2334 [inline]
 __se_sys_clone kernel/fork.c:2328 [inline]
 __x64_sys_clone+0xbf/0x150 kernel/fork.c:2328
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808c2a6580
 which belongs to the cache task_struct(33:syz1) of size 6080
The buggy address is located 224 bytes to the right of
 6080-byte region [ffff88808c2a6580, ffff88808c2a7d40)
The buggy address belongs to the page:
page:ffffea000230a980 count:1 mapcount:0 mapping:ffff888092521040 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea000279fd88 ffffea0001995e88 ffff888092521040
raw: 0000000000000000 ffff88808c2a6580 0000000100000001 ffff888086f8a6c0
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff888086f8a6c0

Memory state around the buggy address:
 ffff88808c2a7d00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff88808c2a7d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88808c2a7e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                               ^
 ffff88808c2a7e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88808c2a7f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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