760d0077ab
[ Upstream commit 81ffd56b5745355b70d54ca4e1bdd0d64a66ff9f ]
Technically this extends the critical section covered by uuid_mutex to:
- parse early mount options -- here we can call device scan on paths
that can be passed as 'device=/dev/...'
- scan the device passed to mount
- open the devices related to the fs_devices -- this increases
fs_devices::opened
The race can happen when mount calls one of the scans and there's
another one called eg. by mkfs or 'btrfs dev scan':
Mount Scan
----- ----
scan_one_device (dev1, fsid1)
scan_one_device (dev2, fsid1)
add the device
free stale devices
fsid1 fs_devices::opened == 0
find fsid1:dev1
free fsid1:dev1
if it's the last one,
free fs_devices of fsid1
too
open_devices (dev1, fsid1)
dev1 not found
When fixed, the uuid mutex will make sure that mount will increase
fs_devices::opened and this will not be touched by the racing scan
ioctl.
Reported-and-tested-by: syzbot+909a5177749d7990ffa4@syzkaller.appspotmail.com
Reported-and-tested-by: syzbot+ceb2606025ec1cc3479c@syzkaller.appspotmail.com
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.