WARNING in __get_user_pages

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b68e78cf BACKPORT: arm64/vdso: Fix nsec handling for CLOCK..
git tree: android-4.4
console output: https://syzkaller.appspot.com/x/log.txt?x=1231bc9e400000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e912d922815a1c1
dashboard link: https://syzkaller.appspot.com/bug?extid=58a351d02f7d1533af1b
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1103eb7a400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11b3ef2e400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+58a351...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 2114 at mm/gup.c:385 check_vma_flags mm/gup.c:385
[inline]()
WARNING: CPU: 1 PID: 2114 at mm/gup.c:385 __get_user_pages+0xa04/0xea0
mm/gup.c:499()
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 2114 Comm: syz-executor246 Not tainted 4.4.154+ #97
0000000000000000 2d9296c0b4aa7ee3 ffff8800b63878f8 ffffffff81a54fed
ffffffff82835440 ffff8800b72ec740 ffffffff82892620 0000000000000009
0000000000000181 ffff8800b63879b8 ffffffff8138a884 0000000041b58ab3
Call Trace:
[<ffffffff81a54fed>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81a54fed>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
[<ffffffff8138a884>] panic+0x19e/0x359 kernel/panic.c:112
[<ffffffff8138aa74>] warn_slowpath_common.cold.6+0x20/0x20
kernel/panic.c:455
[<ffffffff810d17a9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:492
[<ffffffff8140c184>] check_vma_flags mm/gup.c:385 [inline]
[<ffffffff8140c184>] __get_user_pages+0xa04/0xea0 mm/gup.c:499
[<ffffffff8140cd9e>] __get_user_pages_locked mm/gup.c:656 [inline]
[<ffffffff8140cd9e>] get_user_pages+0x8e/0xa0 mm/gup.c:864
[<ffffffff8140e5a4>] __access_remote_vm+0x1e4/0x3c0 mm/memory.c:3735
[<ffffffff81414f88>] access_process_vm+0x58/0x80 mm/memory.c:3813
[<ffffffff810eef92>] generic_ptrace_pokedata kernel/ptrace.c:1145 [inline]
[<ffffffff810eef92>] ptrace_request+0x502/0xbc0 kernel/ptrace.c:861
[<ffffffff8102b487>] arch_ptrace+0x597/0x990 arch/x86/kernel/ptrace.c:923
[<ffffffff810ee911>] SYSC_ptrace kernel/ptrace.c:1118 [inline]
[<ffffffff810ee911>] SyS_ptrace+0xb1/0x140 kernel/ptrace.c:1083
[<ffffffff82690521>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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