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== Problem == Nathan Chancellor reported an oops when aceessing the 'sgx_total_bytes' sysfs file: https://lore.kernel.org/all/YbzhBrimHGGpddDM@archlinux-ax161/ The sysfs output code accesses the sgx_numa_nodes[] array unconditionally. However, this array is allocated during SGX initialization, which only occurs on systems where SGX is supported. If the sysfs file is accessed on systems without SGX support, sgx_numa_nodes[] is NULL and an oops occurs. == Solution == To fix this, hide the entire nodeX/x86/ attribute group on systems without SGX support using the ->is_visible attribute group callback. Unfortunately, SGX is initialized via a device_initcall() which occurs _after_ the ->is_visible() callback. Instead of moving SGX initialization earlier, call sysfs_update_group() during SGX initialization to update the group visiblility. This update requires moving the SGX sysfs code earlier in sgx/main.c. There are no code changes other than the addition of arch_update_sysfs_visibility() and a minor whitespace fixup to arch_node_attr_is_visible() which checkpatch caught. CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-sgx@vger.kernel.org Cc: x86@kernel.org Fixes: 50468e431335 ("x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node") Reported-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/20220104171527.5E8416A8@davehans-spike.ostc.intel.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.