KASAN: use-after-free Read in __isofs_iget

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4e68c9b0763f Linux 4.14.239
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=130ffd02300000
kernel config: https://syzkaller.appspot.com/x/.config?x=9184a6d69099c38
dashboard link: https://syzkaller.appspot.com/bug?extid=4bcdacd12d4f4f7c38dc
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1772dc32300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14f2a124300000

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

isofs: isofs_export_get_parent(): child directory not normalized!
isofs: isofs_export_get_parent(): child directory not normalized!
==================================================================
BUG: KASAN: use-after-free in isofs_read_inode fs/isofs/inode.c:1355 [inline]
BUG: KASAN: use-after-free in __isofs_iget+0x19dd/0x1de0 fs/isofs/inode.c:1555
Read of size 1 at addr ffff88808bd6a015 by task syz-executor181/8027

CPU: 0 PID: 8027 Comm: syz-executor181 Not tainted 4.14.239-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x1b2/0x281 lib/dump_stack.c:58
print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
kasan_report_error.cold+0x8a/0x191 mm/kasan/report.c:351
kasan_report mm/kasan/report.c:409 [inline]
__asan_report_load1_noabort+0x68/0x70 mm/kasan/report.c:427
isofs_read_inode fs/isofs/inode.c:1355 [inline]
__isofs_iget+0x19dd/0x1de0 fs/isofs/inode.c:1555
isofs_iget fs/isofs/isofs.h:134 [inline]
isofs_export_iget fs/isofs/export.c:29 [inline]
isofs_export_iget fs/isofs/export.c:20 [inline]
isofs_fh_to_dentry fs/isofs/export.c:170 [inline]
isofs_fh_to_dentry+0xf7/0x1b0 fs/isofs/export.c:162
exportfs_decode_fh+0x113/0x6c0 fs/exportfs/expfs.c:433
do_handle_to_path fs/fhandle.c:153 [inline]
handle_to_path fs/fhandle.c:208 [inline]
do_handle_open+0x248/0x570 fs/fhandle.c:224
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x444e19
RSP: 002b:00007fff54600378 EFLAGS: 00000246 ORIG_RAX: 0000000000000130
RAX: ffffffffffffffda RBX: 0000000000006ea4 RCX: 0000000000444e19
RDX: 0000000000000000 RSI: 0000000020000040 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: 00007fff546003a0
R10: 00007fff54600240 R11: 0000000000000246 R12: 00007fff5460039c
R13: 00007fff546003d0 R14: 00007fff546003b0 R15: 000000000000000b

The buggy address belongs to the page:
page:ffffea00022f5a80 count:0 mapcount:0 mapping: (null) index:0x1
flags: 0xfff00000000000()
raw: 00fff00000000000 0000000000000000 0000000000000001 00000000ffffffff
raw: ffffea00022f5ae0 ffffea00022f78e0 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808bd69f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88808bd69f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88808bd6a000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88808bd6a080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88808bd6a100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches