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SubjectRe: [PATCH v13 2/2] x86/sgx: Add an attribute for the amount of SGX memory in a NUMA node
On Thu, Jan 06, 2022 at 09:18:35PM +0200, Jarkko Sakkinen wrote:
> On Sat, Jan 01, 2022 at 08:54:51PM -0800, Dave Hansen wrote:
> > On 12/28/21 3:45 PM, Jarkko Sakkinen wrote:
> > >> If I can provide any further information or testing, let me know!
> > > Dave, when is the fix going to be applied [*]?
> > >
> > >> Cheers,
> > >> Nathan
> > > [*] https://lore.kernel.org/linux-sgx/YcGTePmWDMOQU1pn@iki.fi/T/#m831a01bdde347f9e0af2c973986fae0499718201
> >
> > Greg preferred hiding the file as opposed to faking a number in there.
> > Any testing of the attached would be appreciated.
>
> >
> > From: Dave Hansen <dave.hansen@linux.intel.com>
> >
> > 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 <nathan@kernel.org>
> > CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: Jarkko Sakkinen <jarkko@kernel.org>
> > Cc: linux-sgx@vger.kernel.org
> > Cc: x86@kernel.org
> > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> > ---
> >
> > 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 */
> >
> > _
>
> I'm compiling now kernel with this applied, reporting soon but the fix
> looks good to me.

Tested-by: Jarkko Sakkinen <jarkko@kernel.org>

Did two tests in a virtual machine:

1. Without the patch reproduced the crash.
2. With the patch verified that the crash does not occur.

/Jarkko

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