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BUG: KASAN: use-after-free in pskb_may_pull include/linux/skbuff.h:2108 [inline]
BUG: KASAN: use-after-free in skb_ensure_writable+0x554/0x620 net/core/skbuff.c:5118
Read of size 4 at addr ffff8801bb71be80 by task syz-executor3/29122

CPU: 1 PID: 29122 Comm: syz-executor3 Not tainted 4.17.0-rc6+ #31
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+0x1b9/0x294 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 pskb_may_pull include/linux/skbuff.h:2108 [inline]
 skb_ensure_writable+0x554/0x620 net/core/skbuff.c:5118
 __bpf_try_make_writable net/core/filter.c:1606 [inline]
 bpf_try_make_writable net/core/filter.c:1612 [inline]
 ____bpf_l4_csum_replace net/core/filter.c:1822 [inline]
 bpf_l4_csum_replace+0x91/0x4a0 net/core/filter.c:1809

Allocated by task 28103:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
 kmem_cache_zalloc include/linux/slab.h:691 [inline]
 mmap_region+0x9a6/0x1870 mm/mmap.c:1732
 do_mmap+0x9d2/0x12e0 mm/mmap.c:1535
 do_mmap_pgoff include/linux/mm.h:2236 [inline]
 vm_mmap_pgoff+0x1fb/0x2a0 mm/util.c:357
 ksys_mmap_pgoff+0x4c9/0x640 mm/mmap.c:1585
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
 __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 28103:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 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+0x86/0x2d0 mm/slab.c:3756
 remove_vma+0x164/0x1b0 mm/mmap.c:185
 exit_mmap+0x35d/0x5a0 mm/mmap.c:3116
 __mmput kernel/fork.c:961 [inline]
 mmput+0x251/0x610 kernel/fork.c:982
 exit_mm kernel/exit.c:544 [inline]
 do_exit+0xe98/0x2730 kernel/exit.c:852
 do_group_exit+0x16f/0x430 kernel/exit.c:968
 __do_sys_exit_group kernel/exit.c:979 [inline]
 __se_sys_exit_group kernel/exit.c:977 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:977
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801bb71be70
 which belongs to the cache vm_area_struct of size 200
The buggy address is located 16 bytes inside of
 200-byte region [ffff8801bb71be70, ffff8801bb71bf38)
The buggy address belongs to the page:
page:ffffea0006edc6c0 count:1 mapcount:0 mapping:ffff8801bb71b000 index:0xffff8801bb71b318
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801bb71b000 ffff8801bb71b318 000000010000000b
raw: ffffea00074203e0 ffffea0006c74620 ffff8801da97a840 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801bb71bd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801bb71be00: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fb fb
>ffff8801bb71be80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8801bb71bf00: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
 ffff8801bb71bf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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