general protection fault in make_kuid

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    6d21a41b Add linux-next specific files for 20190718
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15200158600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3430a151e1452331
dashboard link: https://syzkaller.appspot.com/bug?extid=7d6a57304857423318a5
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1688da20600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16de4894600000

The bug was bisected to:

commit e786741ff1b52769b044b7f4407f39cd13ee5d2d
Author: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date:   Thu Jul 11 22:36:02 2019 +0000

    Merge tag 'staging-5.3-rc1' of  
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16610cf0600000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=15610cf0600000
console output: https://syzkaller.appspot.com/x/log.txt?x=11610cf0600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+7d6a57304857423318a5@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: e786741ff1b5 ("Merge tag 'staging-5.3-rc1' of  
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging")

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9000 Comm: syz-executor213 Not tainted 5.2.0-next-20190718 #41
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:map_id_range_down+0x87/0x370 /kernel/user_namespace.c:293
Code: 6e 81 c7 00 f1 f1 f1 f1 c7 40 04 00 04 f3 f3 65 48 8b 04 25 28 00 00  
00 48 89 45 d0 31 c0 e8 c0 a5 03 00 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 28  
84 c0 74 08 3c 03 0f 8e 9f 02 00 00 4c 8b ad 68 ff
RSP: 0018:ffff88809a567a30 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88809a567aa8 RCX: ffffffff825b97b5
RDX: 0000000000000000 RSI: ffffffff816edf30 RDI: 0000000000000000
RBP: ffff88809a567ad0 R08: ffff88808e4d2600 R09: ffffed1014af1713
R10: ffffed1014af1712 R11: 0000000000000003 R12: 0000000000000001
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000555555618880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000084 CR3: 000000008b2ec000 CR4: 00000000001406f0
Call Trace:
 map_id_down /kernel/user_namespace.c:312 [inline]
 make_kuid+0x23/0x30 /kernel/user_namespace.c:389
 fuse_parse_param+0x2cb/0x750 /fs/fuse/inode.c:523
 vfs_parse_fs_param+0x2ca/0x540 /fs/fs_context.c:145
 vfs_parse_fs_string+0x105/0x170 /fs/fs_context.c:188
 generic_parse_monolithic+0x181/0x200 /fs/fs_context.c:228
 parse_monolithic_mount_data+0x69/0x90 /fs/fs_context.c:708
 do_remount /fs/namespace.c:2520 [inline]
 do_mount+0x924/0x1c30 /fs/namespace.c:3102
 ksys_mount+0xdb/0x150 /fs/namespace.c:3320
 __do_sys_mount /fs/namespace.c:3334 [inline]
 __se_sys_mount /fs/namespace.c:3331 [inline]
 __x64_sys_mount+0xbe/0x150 /fs/namespace.c:3331
 do_syscall_64+0xfd/0x6a0 /arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4406e9
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:00007ffdf71f73c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000007275 RCX: 00000000004406e9
RDX: 0000000000000000 RSI: 0000000020000100 RDI: 0000000000000000
RBP: 00000000006cb018 R08: 0000000020000300 R09: 65732f636f72702f
R10: 0000000000000070 R11: 0000000000000246 R12: 0000000000401fd0
R13: 0000000000402060 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 4fbbc963024437d2 ]---
RIP: 0010:map_id_range_down+0x87/0x370 /kernel/user_namespace.c:293
Code: 6e 81 c7 00 f1 f1 f1 f1 c7 40 04 00 04 f3 f3 65 48 8b 04 25 28 00 00  
00 48 89 45 d0 31 c0 e8 c0 a5 03 00 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 28  
84 c0 74 08 3c 03 0f 8e 9f 02 00 00 4c 8b ad 68 ff
RSP: 0018:ffff88809a567a30 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88809a567aa8 RCX: ffffffff825b97b5
RDX: 0000000000000000 RSI: ffffffff816edf30 RDI: 0000000000000000
RBP: ffff88809a567ad0 R08: ffff88808e4d2600 R09: ffffed1014af1713
R10: ffffed1014af1712 R11: 0000000000000003 R12: 0000000000000001
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000555555618880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000084 CR3: 000000008b2ec000 CR4: 00000000001406f0


---
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