Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: s390: Revert support for DCACHE_WORD_ACCESS load_unaligned_zeropad() reads eight bytes from unaligned addresses and may cross page boundaries. It handles exceptions which may happen if reading from the second page results in an exception. For pages which are donated to the Ultravisor for secure execution purposes the do_secure_storage_access() exception handler however does not handle such exceptions correctly. Such an exception may result in an endless exception loop which will never be resolved. An attempt to fix this [1] turned out to be not sufficient. For now revert load_unaligned_zeropad() until this problem has been resolved in a proper way. Note that the implementation of load_unaligned_zeropad() itself is correct. The revert is just a temporary workaround until there is complete fix for secure storage access exceptions. [1] commit b00be77302d7 ("s390/mm: Add missing secure storage access fixups for donated memory")

Affected versions

Linux: 802ba53eefc592a6a82231f74e19bafe3256f172 through before c9e0f1517631ac08987f8385817119bccf2f1f12 (git); 802ba53eefc592a6a82231f74e19bafe3256f172 through before be79d285bea70d0edd5015bd487311bfa8cbebc9 (git); 802ba53eefc592a6a82231f74e19bafe3256f172 through before c94806905e02cc8e17a69c822d93c41743b7ffc5 (git); 802ba53eefc592a6a82231f74e19bafe3256f172 through before 37540b8c287fc817bdbd0c62bb75ad6eab0e5d03 (git); 6.7 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.