================================================================== BUG: KASAN: use-after-free in skb_clear_hash include/linux/skbuff.h:1062 [inline] BUG: KASAN: use-after-free in ip_check_defrag net/ipv4/ip_fragment.c:738 [inline] BUG: KASAN: use-after-free in ip_check_defrag+0x571/0x5b0 net/ipv4/ip_fragment.c:703 Write of size 4 at addr ffff8801c604ad1c by task syz-executor0/4698 CPU: 0 PID: 4698 Comm: syz-executor0 Not tainted 4.9.154+ #21 ffff8801db607a68 ffffffff81b47411 0000000000000001 ffffea0007181280 ffff8801c604ad1c 0000000000000004 ffffffff824a4c01 ffff8801db607aa0 ffffffff81502615 0000000000000001 ffff8801c604ad1c ffff8801c604ad1c Call Trace: [ 186.564266] [] __dump_stack lib/dump_stack.c:15 [inline] [ 186.564266] [] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [] print_address_description+0x6f/0x238 mm/kasan/report.c:256 [] kasan_report_error mm/kasan/report.c:355 [inline] [] kasan_report mm/kasan/report.c:412 [inline] [] kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:397 [] __asan_report_store4_noabort+0x17/0x20 mm/kasan/report.c:437 [] skb_clear_hash include/linux/skbuff.h:1062 [inline] [] ip_check_defrag net/ipv4/ip_fragment.c:738 [inline] [] ip_check_defrag+0x571/0x5b0 net/ipv4/ip_fragment.c:703 [] packet_rcv_fanout+0x51e/0x5f0 net/packet/af_packet.c:1458 [] deliver_skb net/core/dev.c:1857 [inline] [] deliver_ptype_list_skb net/core/dev.c:1872 [inline] [] __netif_receive_skb_core+0x9c3/0x2990 net/core/dev.c:4272 [] __netif_receive_skb+0x58/0x1c0 net/core/dev.c:4327 [] process_backlog+0x1e8/0x610 net/core/dev.c:4952 [] napi_poll net/core/dev.c:5253 [inline] [] net_rx_action+0x3aa/0xdd0 net/core/dev.c:5318 [] __do_softirq+0x22d/0x964 kernel/softirq.c:288 [] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:843 [ 186.696998] [] do_softirq.part.0+0x62/0x70 kernel/softirq.c:332 [] do_softirq+0x18/0x20 kernel/softirq.c:320 [] netif_rx_ni+0xbe/0x310 net/core/dev.c:3919 [] tun_get_user+0xcd2/0x2430 drivers/net/tun.c:1330 [] tun_chr_write_iter+0xda/0x190 drivers/net/tun.c:1353 [] do_iter_readv_writev+0x3d9/0x4b0 fs/read_write.c:695 [] do_readv_writev+0x2ed/0x7a0 fs/read_write.c:871 [] vfs_writev+0x89/0xc0 fs/read_write.c:910 [] do_writev+0xe9/0x260 fs/read_write.c:943 [] SYSC_writev fs/read_write.c:1016 [inline] [] SyS_writev+0x28/0x30 fs/read_write.c:1013 [] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb Allocated by task 4698: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57 save_stack mm/kasan/kasan.c:505 [inline] set_track mm/kasan/kasan.c:517 [inline] kasan_kmalloc.part.0+0x62/0xf0 mm/kasan/kasan.c:609 kasan_kmalloc+0xb7/0xd0 mm/kasan/kasan.c:594 kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:547 slab_post_alloc_hook mm/slab.h:417 [inline] slab_alloc_node mm/slub.c:2715 [inline] slab_alloc mm/slub.c:2723 [inline] kmem_cache_alloc+0xd5/0x2b0 mm/slub.c:2728 skb_clone+0x122/0x2a0 net/core/skbuff.c:1034 skb_share_check include/linux/skbuff.h:1428 [inline] ip_check_defrag net/ipv4/ip_fragment.c:725 [inline] ip_check_defrag+0x2d9/0x5b0 net/ipv4/ip_fragment.c:703 packet_rcv_fanout+0x51e/0x5f0 net/packet/af_packet.c:1458 deliver_skb net/core/dev.c:1857 [inline] deliver_ptype_list_skb net/core/dev.c:1872 [inline] __netif_receive_skb_core+0x9c3/0x2990 net/core/dev.c:4272 __netif_receive_skb+0x58/0x1c0 net/core/dev.c:4327 process_backlog+0x1e8/0x610 net/core/dev.c:4952 napi_poll net/core/dev.c:5253 [inline] net_rx_action+0x3aa/0xdd0 net/core/dev.c:5318 __do_softirq+0x22d/0x964 kernel/softirq.c:288 Freed by task 4698: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57 save_stack mm/kasan/kasan.c:505 [inline] set_track mm/kasan/kasan.c:517 [inline] kasan_slab_free+0xb0/0x190 mm/kasan/kasan.c:582 slab_free_hook mm/slub.c:1355 [inline] slab_free_freelist_hook mm/slub.c:1377 [inline] slab_free mm/slub.c:2958 [inline] kmem_cache_free+0xbe/0x310 mm/slub.c:2980 kfree_skbmem+0x9f/0x100 net/core/skbuff.c:623 __kfree_skb net/core/skbuff.c:685 [inline] kfree_skb+0xd4/0x350 net/core/skbuff.c:705 ip_frag_queue net/ipv4/ip_fragment.c:505 [inline] ip_defrag+0x620/0x3bc0 net/ipv4/ip_fragment.c:690 ip_check_defrag net/ipv4/ip_fragment.c:736 [inline] ip_check_defrag+0x3d6/0x5b0 net/ipv4/ip_fragment.c:703 packet_rcv_fanout+0x51e/0x5f0 net/packet/af_packet.c:1458 deliver_skb net/core/dev.c:1857 [inline] deliver_ptype_list_skb net/core/dev.c:1872 [inline] __netif_receive_skb_core+0x9c3/0x2990 net/core/dev.c:4272 __netif_receive_skb+0x58/0x1c0 net/core/dev.c:4327 process_backlog+0x1e8/0x610 net/core/dev.c:4952 napi_poll net/core/dev.c:5253 [inline] net_rx_action+0x3aa/0xdd0 net/core/dev.c:5318 __do_softirq+0x22d/0x964 kernel/softirq.c:288 The buggy address belongs to the object at ffff8801c604ac80 which belongs to the cache skbuff_head_cache of size 224 The buggy address is located 156 bytes inside of 224-byte region [ffff8801c604ac80, ffff8801c604ad60) The buggy address belongs to the page: page:ffffea0007181280 count:1 mapcount:0 mapping: (null) index:0x0 flags: 0x4000000000000080(slab) page dumped because: kasan: bad access detected audit: type=1400 audit(1549139327.379:15): avc: denied { create } for pid=4693 comm="syz-executor1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_fib_lookup_socket permissive=1 Memory state around the buggy address: ffff8801c604ac00: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc ffff8801c604ac80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8801c604ad00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc audit: type=1400 audit(1549139327.379:16): avc: denied { write } for pid=4693 comm="syz-executor1" path="socket:[10205]" dev="sockfs" ino=10205 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_fib_lookup_socket permissive=1 ^ ffff8801c604ad80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb ffff8801c604ae00: fb fb fb fb fb fb fb fb 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