WARNING in __access_remote_vm

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 62872f95 Merge 4.4.174 into android-4.4
git tree: android-4.4
console output: https://syzkaller.appspot.com/x/log.txt?x=11ce99d0a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=47bc4dd423780c4a
dashboard link: https://syzkaller.appspot.com/bug?extid=4b215dbdf9c955ae8e20
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15f1c4e8a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=106cc5d0a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4b215d...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 2080 at mm/gup.c:388 check_vma_flags mm/gup.c:388
[inline]()
WARNING: CPU: 1 PID: 2080 at mm/gup.c:388 __get_user_pages+0xae7/0xfd0
mm/gup.c:502()
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 2080 Comm: syz-executor084 Not tainted 4.4.174+ #17
0000000000000000 a18348917b27171f ffff8801d42bf818 ffffffff81aad1a1
0000000000000000 ffffffff82835ee0 ffffffff82892ea0 0000000000000184
ffffffff8142cb27 ffff8801d42bf8f8 ffffffff813a48c2 0000000041b58ab3
Call Trace:
[<ffffffff81aad1a1>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81aad1a1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
[<ffffffff813a48c2>] panic+0x1b9/0x37b kernel/panic.c:112
[<ffffffff813a4ab9>] warn_slowpath_common kernel/panic.c:455 [inline]
[<ffffffff813a4ab9>] warn_slowpath_common.cold+0x20/0x20 kernel/panic.c:435
[<ffffffff810d3aaa>] warn_slowpath_null+0x2a/0x30 kernel/panic.c:492
[<ffffffff8142cb27>] check_vma_flags mm/gup.c:388 [inline]
[<ffffffff8142cb27>] __get_user_pages+0xae7/0xfd0 mm/gup.c:502
[<ffffffff8142d73d>] __get_user_pages_locked mm/gup.c:654 [inline]
[<ffffffff8142d73d>] get_user_pages+0x6d/0x90 mm/gup.c:864
[<ffffffff8142eef3>] __access_remote_vm+0x1e3/0x3c0 mm/memory.c:3727
[<ffffffff81435a16>] access_remote_vm+0x36/0x50 mm/memory.c:3787
[<ffffffff815eaf68>] mem_rw.isra.0+0x178/0x320 fs/proc/base.c:898
[<ffffffff815eb165>] mem_write+0x55/0x70 fs/proc/base.c:932
[<ffffffff81496916>] __vfs_write+0x116/0x3d0 fs/read_write.c:491
[<ffffffff81498612>] vfs_write+0x182/0x4e0 fs/read_write.c:540
[<ffffffff8149ac4c>] SYSC_write fs/read_write.c:587 [inline]
[<ffffffff8149ac4c>] SyS_write+0xdc/0x1c0 fs/read_write.c:579
[<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330
[inline]
[<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90
arch/x86/entry/common.c:397
[<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a
Kernel Offset: disabled
Rebooting in 86400 seconds..


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