btrfs: dev-replace: properly validate device names

stable inclusion
from stable-v4.19.273
commit 11d7a2e429c02d51e2dc90713823ea8b8d3d3a84
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9E469
CVE: CVE-2024-26791

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.19.y&id=11d7a2e429c02d51e2dc90713823ea8b8d3d3a84

--------------------------------

commit 9845664b9ee47ce7ee7ea93caf47d39a9d4552c4 upstream.

There's a syzbot report that device name buffers passed to device
replace are not properly checked for string termination which could lead
to a read out of bounds in getname_kernel().

Add a helper that validates both source and target device name buffers.
For devid as the source initialize the buffer to empty string in case
something tries to read it later.

This was originally analyzed and fixed in a different way by Edward Adam
Davis (see links).

Link: https://lore.kernel.org/linux-btrfs/000000000000d1a1d1060cc9c5e7@google.com/
Link: https://lore.kernel.org/linux-btrfs/tencent_44CA0665C9836EF9EEC80CB9E7E206DF5206@qq.com/


CC: stable@vger.kernel.org # 4.19+
CC: Edward Adam Davis <eadavis@qq.com>
Reported-and-tested-by:  <syzbot+33f23b49ac24f986c9e8@syzkaller.appspotmail.com>
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Long Li <leo.lilong@huawei.com>