From: Dave Hansen 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. To fix this, hide the entire nodeX/x86/ attribute group on systems without SGX support using the ->is_visible attribute group callback. Fixes: 50468e431335 ("x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node") Reported-by: Nathan Chancellor CC: Greg Kroah-Hartman Cc: Jarkko Sakkinen Cc: linux-sgx@vger.kernel.org Cc: x86@kernel.org Signed-off-by: Dave Hansen --- b/arch/x86/kernel/cpu/sgx/main.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff -puN arch/x86/kernel/cpu/sgx/main.c~sgx-null-ptr arch/x86/kernel/cpu/sgx/main.c --- a/arch/x86/kernel/cpu/sgx/main.c~sgx-null-ptr 2021-12-20 07:56:38.309584807 -0800 +++ b/arch/x86/kernel/cpu/sgx/main.c 2021-12-20 08:17:28.997705149 -0800 @@ -910,6 +910,16 @@ static ssize_t sgx_total_bytes_show(stru } static DEVICE_ATTR_RO(sgx_total_bytes); +static umode_t arch_node_attr_is_visible(struct kobject * kobj, + struct attribute * attr, int idx) +{ + /* Make all x86/ attributes invisible when SGX is not initialized: */ + if (nodes_empty(sgx_numa_mask)) + return 0; + + return attr->mode; +} + static struct attribute *arch_node_dev_attrs[] = { &dev_attr_sgx_total_bytes.attr, NULL, @@ -918,6 +928,7 @@ static struct attribute *arch_node_dev_a const struct attribute_group arch_node_dev_group = { .name = "x86", .attrs = arch_node_dev_attrs, + .is_visible = arch_node_attr_is_visible, }; #endif /* CONFIG_NUMA */ _