In the Linux kernel, the following vulnerability has been resolved:
arm64/gcs: Fix error handling in arch_set_shadow_stack_status()
alloc_gcs() returns an error-encoded pointer on failure, which comes
from do_mmap(), not NULL.
The current NULL check fails to detect errors, which could lead to using
an invalid GCS address.
Use IS_ERR_VALUE() to properly detect errors, consistent with the
check in gcs_alloc_thread_stack().