s390/cio: fix race condition during online processing

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: s390/cio: fix race condition during online processing A race condition exists in ccw_device_set_online() that can cause the online process to fail, leaving the affected device in an inconsistent state. As a result, subsequent attempts to set that device online fail with return code ENODEV. The problem occurs when a path verification request arrives after a wait for final device state completed, but before the result state is evaluated. Fix this by ensuring that the CCW-device lock is held between determining final state and checking result state. Note that since: commit 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers") path verification requests are much more likely to occur during boot, resulting in an increased chance of this race condition occurring.

References

• https://git.kernel.org/stable/c/3076b3c38a704e10df5e143c213653309d532538
• https://git.kernel.org/stable/c/559f3a6333397ab6cd4a696edd65a70b6be62c6e
• https://git.kernel.org/stable/c/2df56f4ea769ff81e51bbb05699989603bde9c49
• https://git.kernel.org/stable/c/a4234decd0fe429832ca81c4637be7248b88b49e
• https://git.kernel.org/stable/c/2d8527f2f911fab84aec04df4788c0c23af3df48