KASAN: slab-out-of-bounds Read in ntfs_attr_find

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Apr 2, 2018, 1:01:03 PM4/2/18
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syzbot hit the following crash on upstream commit
0adb32858b0bddf4ada5f364a84ed60b196dbcda (Sun Apr 1 21:20:27 2018 +0000)
Linux 4.16
syzbot dashboard link:

C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5967192604540928
syzkaller reproducer:
Raw console output:
Kernel config:
compiler: gcc (GCC) 7.1.1 20170620

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Reported-by: syzbot+aed069...@syzkaller.appspotmail.com
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ntfs: (device loop0): is_boot_sector_ntfs(): Invalid end of sector marker.
BUG: KASAN: slab-out-of-bounds in ntfs_attr_find+0x99a/0xa00
Read of size 4 at addr ffff8801d96bfbb5 by task syzkaller786329/4469

CPU: 0 PID: 4469 Comm: syzkaller786329 Not tainted 4.16.0+ #10
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+0x194/0x24d lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report+0x23c/0x360 mm/kasan/report.c:412
__asan_report_load_n_noabort+0xf/0x20 mm/kasan/report.c:443
ntfs_attr_find+0x99a/0xa00 fs/ntfs/attrib.c:613
ntfs_attr_lookup+0x10e1/0x22a0 fs/ntfs/attrib.c:1203
ntfs_read_inode_mount+0x6cd/0x20f0 fs/ntfs/inode.c:1858
ntfs_fill_super+0x13df/0x2fb0 fs/ntfs/super.c:2871
mount_bdev+0x2b7/0x370 fs/super.c:1119
ntfs_mount+0x34/0x40 fs/ntfs/super.c:3065
mount_fs+0x66/0x2d0 fs/super.c:1222
vfs_kern_mount.part.26+0xc6/0x4a0 fs/namespace.c:1037
vfs_kern_mount fs/namespace.c:2509 [inline]
do_new_mount fs/namespace.c:2512 [inline]
do_mount+0xea4/0x2bb0 fs/namespace.c:2842
SYSC_mount fs/namespace.c:3058 [inline]
SyS_mount+0xab/0x120 fs/namespace.c:3035
do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
RIP: 0033:0x442eca
RSP: 002b:00007ffce22e1a98 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000442eca
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffce22e1aa0
RBP: 00000000006cb018 R08: 000000002007e200 R09: 000000000000000a
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000004
R13: 0000000000401dc0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 2834:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
__do_kmalloc_node mm/slab.c:3670 [inline]
__kmalloc_node+0x47/0x70 mm/slab.c:3677
kmalloc_node include/linux/slab.h:554 [inline]
kvmalloc_node+0x99/0xd0 mm/util.c:419
kvmalloc include/linux/mm.h:541 [inline]
seq_buf_alloc fs/seq_file.c:29 [inline]
seq_read+0x7fc/0x1410 fs/seq_file.c:208
__vfs_read+0xef/0xa00 fs/read_write.c:411
vfs_read+0x11e/0x350 fs/read_write.c:447
SYSC_read fs/read_write.c:573 [inline]
SyS_read+0xef/0x220 fs/read_write.c:566
do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287

Freed by task 2834:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
__cache_free mm/slab.c:3486 [inline]
kfree+0xd9/0x260 mm/slab.c:3801
kvfree+0x36/0x60 mm/util.c:438
seq_release fs/seq_file.c:368 [inline]
single_release+0x78/0xb0 fs/seq_file.c:605
__fput+0x327/0x7e0 fs/file_table.c:209
____fput+0x15/0x20 fs/file_table.c:243
task_work_run+0x199/0x270 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x275/0x2f0 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
do_syscall_64+0x6ec/0x940 arch/x86/entry/common.c:292

The buggy address belongs to the object at ffff8801d96be180
which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 2613 bytes to the right of
4096-byte region [ffff8801d96be180, ffff8801d96bf180)
The buggy address belongs to the page:
page:ffffea000765af80 count:1 mapcount:0 mapping:ffff8801d96be180 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d96be180 0000000000000000 0000000100000001
raw: ffffea0006b1b820 ffffea0007622ba0 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d96bfa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801d96bfb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801d96bfb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801d96bfc00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801d96bfc80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

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Nov 28, 2019, 1:52:02 AM11/28/19
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syzbot has bisected this bug to:

commit 9dd068a4b85a68733213c874d08ef768bbec8d01
Author: Matthias Brugger <matthi...@gmail.com>
Date: Fri Jul 31 15:03:13 2015 +0000

soc: mediatek: Fix SCPSYS compilation

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10880f02e00000
start commit: 0adb3285 Linux 4.16
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=12880f02e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=14880f02e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=df0c336cc3b55d45
dashboard link: https://syzkaller.appspot.com/bug?extid=aed06913f36eff9b544e
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1430ded3800000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1533214b800000

Reported-by: syzbot+aed069...@syzkaller.appspotmail.com
Fixes: 9dd068a4b85a ("soc: mediatek: Fix SCPSYS compilation")

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