WARNING in ion_dma_buf_begin_cpu_access

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    a16afaf7928b Merge tag 'for-v4.18' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1480e36f800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=314f2150f36c16ca
dashboard link: https://syzkaller.appspot.com/bug?extid=55b1d9f811650de944c6
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=150b8abf800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1204efdf800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+55b1d9f811650de944c6@xxxxxxxxxxxxxxxxxxxxxxxxx

1965969 pages RAM
0 pages HighMem/MovableOnly
340001 pages reserved
------------[ cut here ]------------
heap->ops->map_kernel should return ERR_PTR on error
WARNING: CPU: 1 PID: 4564 at drivers/staging/android/ion/ion.c:148  
ion_buffer_kmap_get drivers/staging/android/ion/ion.c:147 [inline]
WARNING: CPU: 1 PID: 4564 at drivers/staging/android/ion/ion.c:148  
ion_dma_buf_begin_cpu_access+0x48e/0x5a0  
drivers/staging/android/ion/ion.c:328
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 4564 Comm: syz-executor145 Not tainted 4.17.0+ #93
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+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
RIP: 0010:ion_buffer_kmap_get drivers/staging/android/ion/ion.c:147 [inline]
RIP: 0010:ion_dma_buf_begin_cpu_access+0x48e/0x5a0  
drivers/staging/android/ion/ion.c:328
Code: ff 41 bc ea ff ff ff 89 de e8 8e b0 ba fb 84 db 75 a8 e8 b5 af ba fb  
48 c7 c7 00 05 68 88 c6 05 39 8d d9 03 01 e8 02 c7 86 fb <0f> 0b eb 8c 48  
c7 c7 40 09 ef 88 e8 12 a3 f7 fb e9 15 ff ff ff e8
RSP: 0018:ffff8801ac87fb08 EFLAGS: 00010286
RAX: 0000000000000034 RBX: 0000000000000000 RCX: ffffffff816191ea
RDX: 0000000000000000 RSI: ffffffff8161f4e1 RDI: ffff8801ac87f7e0
RBP: ffff8801ac87fb60 R08: ffff8801d8856480 R09: 0000000000000006
R10: ffff8801d8856480 R11: 0000000000000000 R12: 00000000ffffffea
R13: ffff8801d977d148 R14: 0000000000000001 R15: ffffffff89724b80
 dma_buf_begin_cpu_access+0x7f/0x160 drivers/dma-buf/dma-buf.c:823
 dma_buf_ioctl+0x1aa/0x240 drivers/dma-buf/dma-buf.c:314
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x1cf/0x16f0 fs/ioctl.c:684
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
 __do_sys_ioctl fs/ioctl.c:708 [inline]
 __se_sys_ioctl fs/ioctl.c:706 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440479
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff6df8d2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000440479
RDX: 0000000020fd3ff8 RSI: 0000000040086200 RDI: 0000000000000004
RBP: 00000000006cb018 R08: 0000000000000001 R09: 00007fff6df80031
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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