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BUG: KASAN: slab-use-after-free in napi_gro_frags+0x6e/0x1030
Read of size 8 at addr ffff888026a27a58 by task syz.1.25/6007

CPU: 0 UID: 0 PID: 6007 Comm: syz.1.25 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 napi_gro_frags+0x6e/0x1030
 tun_get_user+0x28cb/0x3e20
 tun_chr_write_iter+0x113/0x200
 vfs_write+0x5c9/0xb30
 ksys_write+0x145/0x250
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3144b8ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f3145ab1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f3144dc5fa0 RCX: 00007f3144b8ebe9
RDX: 000000000000004b RSI: 0000200000000340 RDI: 0000000000000006
RBP: 00007f3144c11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3144dc6038 R14: 00007f3144dc5fa0 R15: 00007ffcc34649f8
 </TASK>

Allocated by task 6007:
 kasan_save_track+0x3e/0x80
 __kasan_mempool_unpoison_object+0xa0/0x170
 napi_skb_cache_get+0x37b/0x6d0
 __alloc_skb+0x11e/0x2d0
 napi_alloc_skb+0x84/0x7d0
 napi_get_frags+0x69/0x140
 tun_get_user+0x77c/0x3e20
 tun_chr_write_iter+0x113/0x200
 vfs_write+0x5c9/0xb30
 ksys_write+0x145/0x250
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6007:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x46/0x50
 __kasan_slab_free+0x5b/0x80
 kmem_cache_free+0x18f/0x400
 skb_pp_cow_data+0xdd8/0x13e0
 do_xdp_generic+0x699/0x11a0
 tun_get_user+0x2523/0x3e20
 tun_chr_write_iter+0x113/0x200
 vfs_write+0x5c9/0xb30
 ksys_write+0x145/0x250
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888026a27980
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 216 bytes inside of
 freed 240-byte region [ffff888026a27980, ffff888026a27a70)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x26a26
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
ksm flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801d6e2a00 ffffea00009c6280 dead000000000003
raw: 0000000000000000 0000000000150015 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801d6e2a00 ffffea00009c6280 dead000000000003
head: 0000000000000000 0000000000150015 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffea00009a8981 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5590, tgid 5590 (dhcpcd), ts 24859425308, free_ts 23369614969
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x21e4/0x22c0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 allocate_slab+0x8a/0x370
 ___slab_alloc+0xbeb/0x1410
 kmem_cache_alloc_node_noprof+0x280/0x3c0
 __alloc_skb+0x112/0x2d0
 netlink_sendmsg+0x5c6/0xb30
 __sock_sendmsg+0x21c/0x270
 ____sys_sendmsg+0x505/0x830
 ___sys_sendmsg+0x21f/0x2a0
 __x64_sys_sendmsg+0x19b/0x260
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5557 tgid 5557 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 rcu_core+0xcab/0x1770
 handle_softirqs+0x286/0x870
 __irq_exit_rcu+0xca/0x1f0
 irq_exit_rcu+0x9/0x30
 sysvec_apic_timer_interrupt+0xa6/0xc0
 asm_sysvec_apic_timer_interrupt+0x1a/0x20

Memory state around the buggy address:
 ffff888026a27900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888026a27980: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888026a27a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
                                                    ^
 ffff888026a27a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888026a27b00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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