BUG: unable to handle kernel paging request in ion_heap_clear_pages

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    419593da Add linux-next specific files for 20191129
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12bfd882e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7c04b0959e75c206
dashboard link: https://syzkaller.appspot.com/bug?extid=be6ccf3081ce8afd1b56
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+be6ccf3081ce8afd1b56@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: unable to handle page fault for address: fffff52002e00000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 21ffee067 P4D 21ffee067 PUD aa11c067 PMD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 3644 Comm: ion_system_heap Not tainted  
5.4.0-next-20191129-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:121 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:135 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:166 [inline]
RIP: 0010:check_memory_region_inline mm/kasan/generic.c:182 [inline]
RIP: 0010:check_memory_region+0x9c/0x1a0 mm/kasan/generic.c:192
Code: c9 4d 0f 49 c1 49 c1 f8 03 45 85 c0 0f 84 10 01 00 00 41 83 e8 01 4e  
8d 44 c0 08 eb 0d 48 83 c0 08 4c 39 c0 0f 84 a7 00 00 00 <48> 83 38 00 74  
ed 4c 8d 40 08 eb 09 48 83 c0 01 49 39 c0 74 53 80
RSP: 0018:ffffc9000c9f7ab8 EFLAGS: 00010212
RAX: fffff52002e00000 RBX: fffff52002e01600 RCX: ffffffff85d5c229
RDX: 0000000000000001 RSI: 000000000000b000 RDI: ffffc90017000000
RBP: ffffc9000c9f7ad0 R08: fffff52002e01600 R09: 0000000000001600
R10: fffff52002e015ff R11: ffffc9001700afff R12: fffff52002e00000
R13: 000000000000b000 R14: 0000000000000000 R15: ffffc9000c9f7d08
FS:  0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffff52002e00000 CR3: 00000000778bd000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 memset+0x24/0x40 mm/kasan/common.c:107
 memset include/linux/string.h:410 [inline]
 ion_heap_clear_pages+0x49/0x70 drivers/staging/android/ion/ion_heap.c:106
 ion_heap_sglist_zero+0x245/0x270 drivers/staging/android/ion/ion_heap.c:130
 ion_heap_buffer_zero+0xf5/0x150 drivers/staging/android/ion/ion_heap.c:145
 ion_system_heap_free+0x1eb/0x250  
drivers/staging/android/ion/ion_system_heap.c:163
 ion_buffer_destroy+0x159/0x2d0 drivers/staging/android/ion/ion.c:93
 ion_heap_deferred_free+0x29d/0x630  
drivers/staging/android/ion/ion_heap.c:239
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
CR2: fffff52002e00000
---[ end trace ee5c63907f1d6f00 ]---
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:121 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:135 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:166 [inline]
RIP: 0010:check_memory_region_inline mm/kasan/generic.c:182 [inline]
RIP: 0010:check_memory_region+0x9c/0x1a0 mm/kasan/generic.c:192
Code: c9 4d 0f 49 c1 49 c1 f8 03 45 85 c0 0f 84 10 01 00 00 41 83 e8 01 4e  
8d 44 c0 08 eb 0d 48 83 c0 08 4c 39 c0 0f 84 a7 00 00 00 <48> 83 38 00 74  
ed 4c 8d 40 08 eb 09 48 83 c0 01 49 39 c0 74 53 80
RSP: 0018:ffffc9000c9f7ab8 EFLAGS: 00010212
RAX: fffff52002e00000 RBX: fffff52002e01600 RCX: ffffffff85d5c229
RDX: 0000000000000001 RSI: 000000000000b000 RDI: ffffc90017000000
RBP: ffffc9000c9f7ad0 R08: fffff52002e01600 R09: 0000000000001600
R10: fffff52002e015ff R11: ffffc9001700afff R12: fffff52002e00000
R13: 000000000000b000 R14: 0000000000000000 R15: ffffc9000c9f7d08
FS:  0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffff52002e00000 CR3: 00000000778bd000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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