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SubjectRe: [PATCH] [v3] x86/sgx: Fix NULL pointer dereference on non-SGX systems
On Tue, Jan 04, 2022 at 09:15:27AM -0800, Dave Hansen wrote:
>
> From: Dave Hansen <dave.hansen@linux.intel.com>
>
> == 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@kernel.org>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Jarkko Sakkinen <jarkko@kernel.org>
> Cc: linux-sgx@vger.kernel.org
> Cc: x86@kernel.org
> ---
>
> b/arch/x86/kernel/cpu/sgx/main.c | 65 ++++++++++++++++++++++++++++-----------
> 1 file changed, 47 insertions(+), 18 deletions(-)

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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