WARNING in ovl_instantiate

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 4d552acf Linux 4.19.34
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16b4892d200000
kernel config: https://syzkaller.appspot.com/x/.config?x=c95a88291f095edd
dashboard link: https://syzkaller.appspot.com/bug?extid=f6d89fa8799c648d0811
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=179aa9e3200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f6d89f...@syzkaller.appspotmail.com

overlayfs: filesystem on './file0' not supported as upperdir
overlayfs: filesystem on './file0' not supported as upperdir
overlayfs: filesystem on './file0' not supported as upperdir
overlayfs: filesystem on './file0' not supported as upperdir
overlayfs: filesystem on './file0' not supported as upperdir
WARNING: CPU: 1 PID: 27341 at fs/overlayfs/dir.c:263
ovl_instantiate+0x293/0x2f0 fs/overlayfs/dir.c:263
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 27341 Comm: syz-executor.5 Not tainted 4.19.34 #2
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+0x172/0x1f0 lib/dump_stack.c:113
panic+0x263/0x51d kernel/panic.c:185
__warn.cold+0x20/0x54 kernel/panic.c:540
report_bug+0x263/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x204/0x360 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:997
RIP: 0010:ovl_instantiate+0x293/0x2f0 fs/overlayfs/dir.c:263
Code: 04 31 ff 89 c3 89 c6 e8 8b 54 1f ff 85 db 75 63 e8 02 53 1f ff 4c 89
e7 45 31 e4 e8 b7 78 64 ff e9 20 ff ff ff e8 ed 52 1f ff <0f> 0b 41 89 dc
e9 11 ff ff ff e8 de 52 1f ff 0f 0b eb 86 48 89 85
RSP: 0018:ffff888087dbfaa0 EFLAGS: 00010293
RAX: ffff88809251a380 RBX: ffffffffffffff8c RCX: ffffffff824be31d
RDX: 0000000000000000 RSI: ffffffff824be453 RDI: 0000000000000007
RBP: ffff888087dbfb78 R08: ffff88809251a380 R09: ffffed1010fb7f2d
R10: ffffed1010fb7f2c R11: 0000000000000003 R12: ffff88807f5b0420
R13: ffff888078d929e0 R14: 0000000000000000 R15: ffff888087dbfb50
ovl_create_over_whiteout fs/overlayfs/dir.c:519 [inline]
ovl_create_or_link+0xac3/0x1210 fs/overlayfs/dir.c:583
ovl_create_object+0x231/0x2c0 fs/overlayfs/dir.c:617
ovl_symlink+0x25/0x30 fs/overlayfs/dir.c:652
vfs_symlink fs/namei.c:4126 [inline]
vfs_symlink+0x378/0x5d0 fs/namei.c:4112
do_symlinkat+0x22b/0x290 fs/namei.c:4153
__do_sys_symlink fs/namei.c:4172 [inline]
__se_sys_symlink fs/namei.c:4170 [inline]
__x64_sys_symlink+0x59/0x80 fs/namei.c:4170
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458c29
Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fc01adbdc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 0000000000458c29
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000020000040
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fc01adbe6d4
R13: 00000000004c74d3 R14: 00000000004dd3a0 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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[syzbot]

syzbot suspects this bug was fixed by commit:

commit f1c5aa5eda08710c2ba619d93126380881fa1114
Author: Amir Goldstein <amir...@gmail.com>
Date: Thu Apr 18 14:42:08 2019 +0000

ovl: detect overlapping layers

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1518fcb6e00000
start commit: 4b0e041c Linux 4.19.35
git tree: linux-4.19.y
kernel config: https://syzkaller.appspot.com/x/.config?x=bb1bcac868b1655e
dashboard link: https://syzkaller.appspot.com/bug?extid=f6d89fa8799c648d0811
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=119c4c90a00000

If the result looks correct, please mark the bug fixed by replying with:

#syz fix: ovl: detect overlapping layers

For information about bisection process see: https://goo.gl/tpsmEJ#bisection