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BUG: KASAN: use-after-free in tls_fill_prepend include/net/tls.h:339 [inline]
BUG: KASAN: use-after-free in tls_push_record+0x1023/0x13e0 net/tls/tls_sw.c:240
Write of size 1 at addr ffff88019c57c0cb by task syz-executor2/13815

CPU: 0 PID: 13815 Comm: syz-executor2 Not tainted 4.17.0-rc6+ #73
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_store1_noabort+0x17/0x20 mm/kasan/report.c:435
 tls_fill_prepend include/net/tls.h:339 [inline]
 tls_push_record+0x1023/0x13e0 net/tls/tls_sw.c:240
 tls_sw_sendmsg+0x9de/0x12b0 net/tls/tls_sw.c:484
 inet_sendmsg+0x19f/0x690 net/ipv4/af_inet.c:798
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:639
 __sys_sendto+0x3d7/0x670 net/socket.c:1789
 __do_sys_sendto net/socket.c:1801 [inline]
 __se_sys_sendto net/socket.c:1797 [inline]
 __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1797
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455a09
RSP: 002b:00007fef4f017c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007fef4f0186d4 RCX: 0000000000455a09
RDX: 00000000fffffdef RSI: 00000000200005c0 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000020000000 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000005d8 R14: 00000000006fdce0 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea0006715f00 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 dead000000000200 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88019c57bf80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88019c57c000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88019c57c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88019c57c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88019c57c180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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