WARNING in iov_iter_revert

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    427fbe89261d Merge branch 'next' of git://git.kernel.org/p..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b33477800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fcce42b221691ff9
dashboard link: https://syzkaller.appspot.com/bug?extid=c226690f7b3126c5ee04
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=144f1997800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=141d5417800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c226690f7b3126c5ee04@xxxxxxxxxxxxxxxxxxxxxxxxx

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
WARNING: CPU: 1 PID: 4542 at lib/iov_iter.c:857 iov_iter_revert+0x2ee/0xaa0  
lib/iov_iter.c:857
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 4542 Comm: syz-executor650 Not tainted 4.17.0-rc4+ #44
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
 panic+0x22f/0x4de kernel/panic.c:184
 __warn.cold.8+0x163/0x1b3 kernel/panic.c:536
 report_bug+0x252/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x1de/0x490 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
RIP: 0010:iov_iter_revert+0x2ee/0xaa0 lib/iov_iter.c:857
RSP: 0018:ffff8801ad1bf700 EFLAGS: 00010293
RAX: ffff8801ac55e6c0 RBX: 00000000ffffffff RCX: ffffffff835104a1
RDX: 0000000000000000 RSI: ffffffff8351074e RDI: 0000000000000007
RBP: ffff8801ad1bf760 R08: ffff8801ac55e6c0 R09: ffffed003b5e46c2
R10: 0000000000000003 R11: 0000000000000001 R12: 0000000000000001
R13: ffff8801ad1bfd60 R14: 0000000000000011 R15: ffff8801ae9ac040
 tls_sw_sendmsg+0xf1c/0x12d0 net/tls/tls_sw.c:448
 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_sendmsg+0x805/0x940 net/socket.c:2117
 __sys_sendmsg+0x115/0x270 net/socket.c:2155
 __do_sys_sendmsg net/socket.c:2164 [inline]
 __se_sys_sendmsg net/socket.c:2162 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4403a9
RSP: 002b:00007ffdcdfbd6c8 EFLAGS: 00000207 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004403a9
RDX: 0000000000000000 RSI: 0000000020001340 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 000000000000001c R09: 000000000000001c
R10: 0000000020000180 R11: 0000000000000207 R12: 0000000000401cd0
R13: 0000000000401d60 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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