On Sat, Dec 18, 2021 at 12:15:40AM +0100, Greg KH wrote: > On Fri, Dec 17, 2021 at 02:31:53PM -0800, Dave Hansen wrote: > > > > From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > > > > 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. > > > > Add a check to ensure that SGX has been initialized to the point > > where sgx_numa_nodes[] is allocated, before accessing it. > > > > Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx> > > CC: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > Cc: Jarkko Sakkinen <jarkko@xxxxxxxxxx> > > Cc: linux-sgx@xxxxxxxxxxxxxxx > > Cc: x86@xxxxxxxxxx > > Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > > --- > > > > b/arch/x86/kernel/cpu/sgx/main.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > 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 2021-12-17 13:38:00.217312383 -0800 > > +++ b/arch/x86/kernel/cpu/sgx/main.c 2021-12-17 14:00:36.293044390 -0800 > > @@ -906,7 +906,13 @@ 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); > > + unsigned long node_bytes = 0; > > + > > + /* Avoid acccessing sgx_numa_nodes[] when it is not allocated: */ > > + if (!nodes_empty(sgx_numa_mask)) > > + node_bytes = sgx_numa_nodes[dev->id].size; > > + > > + return sysfs_emit(buf, "%lu\n", node_bytes); > > } > > Why is this file showing up if we do not have sgx_numa_nodes not > allocated? It shouldn't even be there to access then. > > don't return a fake number, just don't present the sysfs file at all. Or, if you _have_ to have the file present, return an error instead of a fake value. But really, only create the file if the system supports it, that's the rule for sysfs and it makes it very easy to do so (see the is_visible callback for the attribute group for how to do it.) thanks, greg k-h
