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Subject[PATCH 5.8 86/99] btrfs: fix put of uninitialized kobject after seed device delete
Date
From: Anand Jain <anand.jain@oracle.com>

commit b5ddcffa37778244d5e786fe32f778edf2bfc93e upstream.

The following test case leads to NULL kobject free error:

mount seed /mnt
add sprout to /mnt
umount /mnt
mount sprout to /mnt
delete seed

kobject: '(null)' (00000000dd2b87e4): is not initialized, yet kobject_put() is being called.
WARNING: CPU: 1 PID: 15784 at lib/kobject.c:736 kobject_put+0x80/0x350
RIP: 0010:kobject_put+0x80/0x350
::
Call Trace:
btrfs_sysfs_remove_devices_dir+0x6e/0x160 [btrfs]
btrfs_rm_device.cold+0xa8/0x298 [btrfs]
btrfs_ioctl+0x206c/0x22a0 [btrfs]
ksys_ioctl+0xe2/0x140
__x64_sys_ioctl+0x1e/0x29
do_syscall_64+0x96/0x150
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f4047c6288b
::

This is because, at the end of the seed device-delete, we try to remove
the seed's devid sysfs entry. But for the seed devices under the sprout
fs, we don't initialize the devid kobject yet. So add a kobject state
check, which takes care of the bug.

Fixes: 668e48af7a94 ("btrfs: sysfs, add devid/dev_state kobject and device attributes")
CC: stable@vger.kernel.org # 5.6+
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/sysfs.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -1165,10 +1165,12 @@ int btrfs_sysfs_remove_devices_dir(struc
disk_kobj->name);
}

- kobject_del(&one_device->devid_kobj);
- kobject_put(&one_device->devid_kobj);
+ if (one_device->devid_kobj.state_initialized) {
+ kobject_del(&one_device->devid_kobj);
+ kobject_put(&one_device->devid_kobj);

- wait_for_completion(&one_device->kobj_unregister);
+ wait_for_completion(&one_device->kobj_unregister);
+ }

return 0;
}
@@ -1181,10 +1183,12 @@ int btrfs_sysfs_remove_devices_dir(struc
sysfs_remove_link(fs_devices->devices_kobj,
disk_kobj->name);
}
- kobject_del(&one_device->devid_kobj);
- kobject_put(&one_device->devid_kobj);
+ if (one_device->devid_kobj.state_initialized) {
+ kobject_del(&one_device->devid_kobj);
+ kobject_put(&one_device->devid_kobj);

- wait_for_completion(&one_device->kobj_unregister);
+ wait_for_completion(&one_device->kobj_unregister);
+ }
}

return 0;

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