On Tue, Jan 04, 2022 at 09:15:27AM -0800, Dave Hansen wrote: > > From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > > == 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. > > Fixes: 50468e431335 ("x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node") > Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx> > Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > CC: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: Jarkko Sakkinen <jarkko@xxxxxxxxxx> > Cc: linux-sgx@xxxxxxxxxxxxxxx > Cc: x86@xxxxxxxxxx Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx> > --- > > b/arch/x86/kernel/cpu/sgx/main.c | 65 ++++++++++++++++++++++++++++----------- > 1 file changed, 47 insertions(+), 18 deletions(-) > > 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 2022-01-04 08:43:17.042821249 -0800 > @@ -6,11 +6,13 @@ > #include <linux/highmem.h> > #include <linux/kthread.h> > #include <linux/miscdevice.h> > +#include <linux/node.h> > #include <linux/pagemap.h> > #include <linux/ratelimit.h> > #include <linux/sched/mm.h> > #include <linux/sched/signal.h> > #include <linux/slab.h> > +#include <linux/sysfs.h> > #include <asm/sgx.h> > #include "driver.h" > #include "encl.h" > @@ -780,6 +782,48 @@ static inline u64 __init sgx_calc_sectio > ((high & GENMASK_ULL(19, 0)) << 32); > } > > +#ifdef CONFIG_NUMA > +static ssize_t sgx_total_bytes_show(struct device *dev, struct device_attribute *attr, char *buf) > +{ > + return sysfs_emit(buf, "%lu\n", sgx_numa_nodes[dev->id].size); > +} > +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, > +}; > + > +const struct attribute_group arch_node_dev_group = { > + .name = "x86", > + .attrs = arch_node_dev_attrs, > + .is_visible = arch_node_attr_is_visible, > +}; > + > +static void __init arch_update_sysfs_visibility(int nid) > +{ > + struct node *node = node_devices[nid]; > + int ret; > + > + ret = sysfs_update_group(&node->dev.kobj, &arch_node_dev_group); > + > + if (ret) > + pr_err("sysfs update failed (%d), files may be invisible", ret); > +} > +#else /* !CONFIG_NUMA */ > +static void __init arch_update_sysfs_visibility(int nid) {} > +#endif > + > static bool __init sgx_page_cache_init(void) > { > u32 eax, ebx, ecx, edx, type; > @@ -826,6 +870,9 @@ static bool __init sgx_page_cache_init(v > INIT_LIST_HEAD(&sgx_numa_nodes[nid].sgx_poison_page_list); > node_set(nid, sgx_numa_mask); > sgx_numa_nodes[nid].size = 0; > + > + /* Make SGX-specific node sysfs files visible: */ > + arch_update_sysfs_visibility(nid); > } > > sgx_epc_sections[i].node = &sgx_numa_nodes[nid]; > @@ -903,24 +950,6 @@ int sgx_set_attribute(unsigned long *all > } > EXPORT_SYMBOL_GPL(sgx_set_attribute); > > -#ifdef CONFIG_NUMA > -static ssize_t sgx_total_bytes_show(struct device *dev, struct device_attribute *attr, char *buf) > -{ > - return sysfs_emit(buf, "%lu\n", sgx_numa_nodes[dev->id].size); > -} > -static DEVICE_ATTR_RO(sgx_total_bytes); > - > -static struct attribute *arch_node_dev_attrs[] = { > - &dev_attr_sgx_total_bytes.attr, > - NULL, > -}; > - > -const struct attribute_group arch_node_dev_group = { > - .name = "x86", > - .attrs = arch_node_dev_attrs, > -}; > -#endif /* CONFIG_NUMA */ > - > static int __init sgx_init(void) > { > int ret; > _
