WARNING in kernfs_create_dir_ns

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 4b972a01 Linux 5.2-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14910879a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9a31528e58cc12e2
dashboard link: https://syzkaller.appspot.com/bug?extid=38f5d5cf7ae88c46b11a
compiler: clang version 9.0.0 (/home/glider/llvm/clang
80fee25776c2fb61e74c1ecb1a523375c2500b69)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+38f5d5...@syzkaller.appspotmail.com

WARNING: CPU: 0 PID: 9071 at fs/kernfs/dir.c:493 kernfs_get
fs/kernfs/dir.c:493 [inline]
WARNING: CPU: 0 PID: 9071 at fs/kernfs/dir.c:493 kernfs_new_node
fs/kernfs/dir.c:700 [inline]
WARNING: CPU: 0 PID: 9071 at fs/kernfs/dir.c:493
kernfs_create_dir_ns+0x205/0x230 fs/kernfs/dir.c:1022
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 9071 Comm: syz-executor.1 Not tainted 5.2.0-rc6 #6
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+0x1d8/0x2f8 lib/dump_stack.c:113
panic+0x28a/0x7c9 kernel/panic.c:219
__warn+0x216/0x220 kernel/panic.c:576
report_bug+0x190/0x290 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:179 [inline]
do_error_trap+0xd7/0x450 arch/x86/kernel/traps.c:272
do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:291
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:986
RIP: 0010:kernfs_get fs/kernfs/dir.c:493 [inline]
RIP: 0010:kernfs_new_node fs/kernfs/dir.c:700 [inline]
RIP: 0010:kernfs_create_dir_ns+0x205/0x230 fs/kernfs/dir.c:1022
Code: ff 4c 89 ff e8 7c cd ff ff 4c 63 fb eb 05 e8 e2 27 9a ff 4c 89 f8 48
83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 cb 27 9a ff <0f> 0b e9 e9 fe
ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c be fe ff
RSP: 0018:ffff88805a66f590 EFLAGS: 00010287
RAX: ffffffff81db8a25 RBX: ffff88808fad88c0 RCX: 0000000000040000
RDX: ffffc90007ff6000 RSI: 000000000001e1a2 RDI: 000000000001e1a3
RBP: ffff88805a66f5c8 R08: ffffffff81db8907 R09: ffffed1011f5b119
R10: ffffed1011f5b119 R11: 1ffff11011f5b118 R12: ffff888098366600
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff8880a8f66620
sysfs_create_dir_ns+0x161/0x300 fs/sysfs/dir.c:59
create_dir lib/kobject.c:89 [inline]
kobject_add_internal+0x459/0xd50 lib/kobject.c:255
kobject_add_varg lib/kobject.c:390 [inline]
kobject_add+0x138/0x200 lib/kobject.c:442
device_add+0x508/0x1570 drivers/base/core.c:2062
hci_register_dev+0x331/0x6c0 net/bluetooth/hci_core.c:3305
hci_uart_register_dev drivers/bluetooth/hci_ldisc.c:661 [inline]
hci_uart_set_proto drivers/bluetooth/hci_ldisc.c:685 [inline]
hci_uart_tty_ioctl+0x815/0x970 drivers/bluetooth/hci_ldisc.c:739
tty_ioctl+0xf66/0x15d0 drivers/tty/tty_io.c:2664
do_vfs_ioctl+0x7d4/0x1890 fs/ioctl.c:46
ksys_ioctl fs/ioctl.c:713 [inline]
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0xe3/0x120 fs/ioctl.c:718
do_syscall_64+0xfe/0x140 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459519
Code: fd b7 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb578425c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459519
RDX: 0000000000000009 RSI: 00000000400455c8 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb5784266d4
R13: 00000000004c21a5 R14: 00000000004d5330 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug 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 bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 72825454 Merge branch 'x86-urgent-for-linus' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=104d6755a00000

kernel config: https://syzkaller.appspot.com/x/.config?x=9a31528e58cc12e2
dashboard link: https://syzkaller.appspot.com/bug?extid=38f5d5cf7ae88c46b11a
compiler: clang version 9.0.0 (/home/glider/llvm/clang
80fee25776c2fb61e74c1ecb1a523375c2500b69)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12a6c439a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1353c323a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+38f5d5...@syzkaller.appspotmail.com

WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_get
fs/kernfs/dir.c:493 [inline]
WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_new_node
fs/kernfs/dir.c:700 [inline]
WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493

kernfs_create_dir_ns+0x205/0x230 fs/kernfs/dir.c:1022
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 8613 Comm: syz-executor696 Not tainted 5.2.0-rc6+ #11

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+0x1d8/0x2f8 lib/dump_stack.c:113
panic+0x28a/0x7c9 kernel/panic.c:219
__warn+0x216/0x220 kernel/panic.c:576
report_bug+0x190/0x290 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:179 [inline]
do_error_trap+0xd7/0x450 arch/x86/kernel/traps.c:272
do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:291
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:986
RIP: 0010:kernfs_get fs/kernfs/dir.c:493 [inline]
RIP: 0010:kernfs_new_node fs/kernfs/dir.c:700 [inline]
RIP: 0010:kernfs_create_dir_ns+0x205/0x230 fs/kernfs/dir.c:1022

Code: ff 4c 89 ff e8 7c cd ff ff 4c 63 fb eb 05 e8 22 27 9a ff 4c 89 f8 48
83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 0b 27 9a ff <0f> 0b e9 e9 fe

ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c be fe ff

RSP: 0018:ffff88808d26f730 EFLAGS: 00010293
RAX: ffffffff81db8a95 RBX: ffff88809e5252a0 RCX: ffff88808a4aa000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88808d26f768 R08: ffffffff81db8977 R09: ffffed1013ca4a55
R10: ffffed1013ca4a55 R11: 1ffff11013ca4a54 R12: ffff888098a8a200
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff8880a339e620

sysfs_create_dir_ns+0x161/0x300 fs/sysfs/dir.c:59
create_dir lib/kobject.c:89 [inline]
kobject_add_internal+0x459/0xd50 lib/kobject.c:255
kobject_add_varg lib/kobject.c:390 [inline]
kobject_add+0x138/0x200 lib/kobject.c:442
device_add+0x508/0x1570 drivers/base/core.c:2062
hci_register_dev+0x331/0x6c0 net/bluetooth/hci_core.c:3305

__vhci_create_device drivers/bluetooth/hci_vhci.c:124 [inline]
vhci_create_device+0x2d1/0x510 drivers/bluetooth/hci_vhci.c:148
vhci_get_user drivers/bluetooth/hci_vhci.c:204 [inline]
vhci_write+0x3ac/0x440 drivers/bluetooth/hci_vhci.c:284
call_write_iter include/linux/fs.h:1872 [inline]
new_sync_write fs/read_write.c:483 [inline]
__vfs_write+0x617/0x7d0 fs/read_write.c:496
vfs_write+0x227/0x510 fs/read_write.c:558
ksys_write+0x16b/0x2a0 fs/read_write.c:611
__do_sys_write fs/read_write.c:623 [inline]
__se_sys_write fs/read_write.c:620 [inline]
__x64_sys_write+0x7b/0x90 fs/read_write.c:620
do_syscall_64+0xfe/0x140 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x441279
Code: e8 ac e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 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 eb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffa3738588 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441279
RDX: 0000000000000002 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 000000000000ef5c R08: 00000000004002c8 R09: 00000000004002c8
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000401ff0
R13: 0000000000402080 R14: 0000000000000000 R15: 0000000000000000

[syzbot]

syzbot has bisected this bug to:

commit 7f38abf220e2c800a2c451372e9f07ed5fd0ea49
Author: Hongjie Fang <hongj...@asrmicro.com>
Date: Tue Jul 31 02:55:09 2018 +0000

mmc: core: improve reasonableness of bus width setting for HS400es

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=129d6755a00000
start commit: 72825454 Merge branch 'x86-urgent-for-linus' of git://git...
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=119d6755a00000
console output: https://syzkaller.appspot.com/x/log.txt?x=169d6755a00000

kernel config: https://syzkaller.appspot.com/x/.config?x=9a31528e58cc12e2
dashboard link: https://syzkaller.appspot.com/bug?extid=38f5d5cf7ae88c46b11a

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12a6c439a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1353c323a00000

Reported-by: syzbot+38f5d5...@syzkaller.appspotmail.com
Fixes: 7f38abf220e2 ("mmc: core: improve reasonableness of bus width
setting for HS400es")

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

[Tejun Heo]

Hello,

On Mon, Jul 01, 2019 at 01:52:35PM +0800, Hillf Danton wrote:
> >WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_get fs/kernfs/dir.c:493 [inline]
> >WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_new_node fs/kernfs/dir.c:700 [inline]
> >WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_create_dir_ns+0x205/0x230 fs/kernfs/dir.c:1022

...
> --- a/fs/sysfs/dir.c
> +++ b/fs/sysfs/dir.c
> @@ -53,6 +53,10 @@ int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
> if (!parent)
> return -ENOENT;
>
> + /* create dir if parent is not dying */
> + if (!atomic_inc_not_zero(&parent->count))
> + return -ENOENT;
> +
> kobject_get_ownership(kobj, &uid, &gid);
>
> kn = kernfs_create_dir_ns(parent, kobject_name(kobj),
> @@ -61,10 +65,12 @@ int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
> if (IS_ERR(kn)) {
> if (PTR_ERR(kn) == -EEXIST)
> sysfs_warn_dup(parent, kobject_name(kobj));
> + kernfs_put(parent);
> return PTR_ERR(kn);
> }
>
> kobj->sd = kn;
> + kernfs_put(parent);

I don't think this is the correct fix. It's being called with kobj
whose parent's sysfs node is dangling. It gotta be fixed from the
caller side.

Thanks.

--
tejun

[Hillf Danton]

Hello,

On Mon, 8 Jul 2019 22:46:38 +0800 Tejun Heo wrote:
> On Mon, Jul 01, 2019 at 01:52:35PM +0800, Hillf Danton wrote:
> > >WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_get fs/kernfs/dir.c:493 [inline]
> > >WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_new_node fs/kernfs/dir.c:700 [inline]
> > >WARNING: CPU: 0 PID: 8613 at fs/kernfs/dir.c:493 kernfs_create_dir_ns+0x205/0x230 fs/kernfs/dir.c:1022
> ...
>

> I don't think this is the correct fix. It's being called with kobj
> whose parent's sysfs node is dangling. It gotta be fixed from the
> caller side.
>

Make sense?

--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -237,15 +237,17 @@ static int kobject_add_internal(struct kobject *kobj)
return -EINVAL;
}

- parent = kobject_get(kobj->parent);
+ parent = kobject_get_unless_zero(kobj->parent);

/* join kset if set, use it as parent if we do not already have one */
if (kobj->kset) {
if (!parent)
- parent = kobject_get(&kobj->kset->kobj);
+ parent = kobject_get_unless_zero(&kobj->kset->kobj);
kobj_kset_join(kobj);
kobj->parent = parent;
}
+ if (!parent)
+ return -ENOENT;

pr_debug("kobject: '%s' (%p): %s: parent: '%s', set: '%s'\n",
kobject_name(kobj), kobj, __func__,
--

[Tejun Heo]

On Tue, Jul 09, 2019 at 10:23:35AM +0800, Hillf Danton wrote:
> > I don't think this is the correct fix. It's being called with kobj
> > whose parent's sysfs node is dangling. It gotta be fixed from the
> > caller side.
> >
> Make sense?
>
> --- a/lib/kobject.c
> +++ b/lib/kobject.c

No, I meant that the problem likely is in the driver which is calling
into the generic layer with a dead parent. We shouldn't be working
around that from generic layer.

Thanks.

--
tejun

[syzbot]

syzbot suspects this bug was fixed by commit:

commit 810507fe6fd5ff3de429121adff49523fabb643a
Author: Waiman Long <lon...@redhat.com>
Date: Thu Feb 6 15:24:08 2020 +0000

locking/lockdep: Reuse freed chain_hlocks entries

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1008138be00000

start commit: 72825454 Merge branch 'x86-urgent-for-linus' of git://git...
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=9a31528e58cc12e2
dashboard link: https://syzkaller.appspot.com/bug?extid=38f5d5cf7ae88c46b11a

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12a6c439a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1353c323a00000

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

#syz fix: locking/lockdep: Reuse freed chain_hlocks entries

[Waiman Long]