[syzbot] BUG: unable to handle kernel NULL pointer dereference in __d_instantiate

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a6b443748715 Merge branch 'for-next/core', remote-tracking..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=16271d4f080000
kernel config: https://syzkaller.appspot.com/x/.config?x=e79d82586727c5df
dashboard link: https://syzkaller.appspot.com/bug?extid=29dc75ed37be943c610e
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=162474a7080000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=119b6b78880000

Downloadable assets:
disk image: https://storage.googleapis.com/1436897f0dc0/disk-a6b44374.raw.xz
vmlinux: https://storage.googleapis.com/68c4de151fbb/vmlinux-a6b44374.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+29dc75...@syzkaller.appspotmail.com

ntfs3: loop0: Different NTFS' sector size (1024) and media sector size (512)
ntfs3: loop0: RAW NTFS volume: Filesystem size 0.00 Gb > volume size 0.00 Gb. Mount in read-only
ntfs3: loop0: Failed to load $Extend.
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0
user pgtable: 4k pages, 48-bit VAs, pgdp=0000000109094000
[0000000000000008] pgd=080000010aed9003, p4d=080000010aed9003, pud=080000010738d003, pmd=0000000000000000
Internal error: Oops: 96000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 3027 Comm: syz-executor119 Not tainted 6.0.0-rc4-syzkaller-17255-ga6b443748715 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : d_flags_for_inode fs/dcache.c:1980 [inline]
pc : __d_instantiate+0x2a0/0x2e4 fs/dcache.c:1998
lr : d_flags_for_inode fs/dcache.c:1979 [inline]
lr : __d_instantiate+0x80/0x2e4 fs/dcache.c:1998
sp : ffff8000126f3ac0
x29: ffff8000126f3ac0 x28: 0000000040000000 x27: ffff0000cd3a0000
x26: ffff80000cf0e000 x25: fffffc0000000000 x24: 000000000001f000
x23: ffff0000cd3a0000 x22: 0000000000000008 x21: 0000000000000000
x20: ffff0000ca50ce48 x19: ffff0000c7732750 x18: 00000000000000c0
x17: ffff80000dd3a698 x16: ffff80000db78658 x15: ffff0000c4f13500
x14: 00000000000000b8 x13: 00000000ffffffff x12: ffff0000c4f13500
x11: ff808000085e2a88 x10: 0000000000000000 x9 : ffff0000c4f13500
x8 : 0000000000000000 x7 : ffff8000085e2e0c x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 0000000000000001 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
d_flags_for_inode fs/dcache.c:1980 [inline]
__d_instantiate+0x2a0/0x2e4 fs/dcache.c:1998
d_instantiate fs/dcache.c:2036 [inline]
d_make_root+0x64/0xa8 fs/dcache.c:2071
ntfs_fill_super+0x1420/0x14a4 fs/ntfs/super.c:180
get_tree_bdev+0x1e8/0x2a0 fs/super.c:1323
ntfs_fs_get_tree+0x28/0x38 fs/ntfs3/super.c:1358
vfs_get_tree+0x40/0x140 fs/super.c:1530
do_new_mount+0x1dc/0x4e4 fs/namespace.c:3040
path_mount+0x358/0x914 fs/namespace.c:3370
do_mount fs/namespace.c:3383 [inline]
__do_sys_mount fs/namespace.c:3591 [inline]
__se_sys_mount fs/namespace.c:3568 [inline]
__arm64_sys_mount+0x2f8/0x408 fs/namespace.c:3568
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:624
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:642
el0t_64_sync+0x18c/0x190
Code: 79000688 52a00417 17ffff83 f9401288 (f9400508)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 79000688 strh w8, [x20, #2]
4: 52a00417 mov w23, #0x200000 // #2097152
8: 17ffff83 b 0xfffffffffffffe14
c: f9401288 ldr x8, [x20, #32]
* 10: f9400508 ldr x8, [x8, #8] <-- trapping instruction


---
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[Andreas Dilger]

> On Sep 13, 2022, at 1:51 PM, syzbot <syzbot+29dc75...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:

This is almost certainly an NTFS3 error handling bug due to mounting the
broken filesystem image, but the NTFS3 maintainer and list were not CC'd.

Cheers, Andreas

Cheers, Andreas

[Al Viro]

On Tue, Sep 13, 2022 at 12:51:42PM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: a6b443748715 Merge branch 'for-next/core', remote-tracking..
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=16271d4f080000
> kernel config: https://syzkaller.appspot.com/x/.config?x=e79d82586727c5df
> dashboard link: https://syzkaller.appspot.com/bug?extid=29dc75ed37be943c610e
> compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: arm64
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=162474a7080000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=119b6b78880000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/1436897f0dc0/disk-a6b44374.raw.xz
> vmlinux: https://storage.googleapis.com/68c4de151fbb/vmlinux-a6b44374.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+29dc75...@syzkaller.appspotmail.com
>
> ntfs3: loop0: Different NTFS' sector size (1024) and media sector size (512)
> ntfs3: loop0: RAW NTFS volume: Filesystem size 0.00 Gb > volume size 0.00 Gb. Mount in read-only
> ntfs3: loop0: Failed to load $Extend.
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008

at a guess - bollocksed inode; NULL ->i_op (should never happen; it takes actively
assigning NULL to it, but apparently ntfs_read_mft() is that dumb), combined with
candidate root inode somehow having S_IFLNK in ->i_mode.

At the very least,
inode->i_op = NULL;
should *NEVER* be done; there is no legitimate reason to do that, no matter
what. ->i_op initially points to empty method table; it should never
point to anything that is not an object of type struct inode_operations.
In particular, it should never become NULL.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 54e45702b648b7c0000e90b3e9b890e367e16ea8
Author: Edward Lo <edwa...@ambergroup.io>
Date: Thu Sep 22 16:50:23 2022 +0000

fs/ntfs3: Validate resident attribute name

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12403c74680000
start commit: f9ff5644bcc0 Merge tag 'hsi-for-6.2' of git://git.kernel.o..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=c163713cf9186fe7
dashboard link: https://syzkaller.appspot.com/bug?extid=29dc75ed37be943c610e
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1077def7880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10175baf880000

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

#syz fix: fs/ntfs3: Validate resident attribute name

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

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.