In the Linux kernel 4.19 through 5.6.7 on the s390 platform, code execution may occur because of a race condition, as demonstrated by code in enable_sacf_uaccess in arch/s390/lib/uaccess.c that fails to protect against a concurrent page table upgrade, aka CID-3f777e19d171. A crash could also occur.
https://security.netapp.com/advisory/ntap-20200608-0001/
https://usn.ubuntu.com/4342-1/
https://usn.ubuntu.com/4343-1/