In the Linux kernel, the following vulnerability has been resolved:
s390/dasd: fix Oops in dasdaliasgetstartdev due to missing pavgroup
Fix Oops in dasdaliasgetstartdev() function caused by the pavgroup pointer being NULL.
The pavgroup pointer is checked on the entrance of the function but without the lcu->lock being held. Therefore there is a race window between dasdaliasgetstartdev() and lcuupdate() which sets pavgroup to NULL with the lcu->lock held.
Fix by checking the pavgroup pointer with lcu->lock held.