From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8336F2CA1 for ; Fri, 7 Jan 2022 11:53:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D6A9AC36AE5; Fri, 7 Jan 2022 11:53:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1641556419; bh=uo4WZxRwd3p3Bnx7jX/0q2Y2n3W/q54d6WDL9IjTF0k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=m/McJmExy6m1HgrSmvW8Ef8OjVr/3GUYuAuhkRug7yZeJCW5X88O0jF9EkEjT+aJR qG0BtrIN0I7V+h0p3AWNmgg9U5aWnQi4ukye+JX9NJ8ZJGxEDNxU1anIe/O2bvKwUd g0YCwxADs7oAWEAB+yynvgwm1FiseTdLhE5qlApxeWNuFe03DOAP4+vnpgu6+RKPjI EY0NAaWvH1ZFsMqRWSTL8gjUS3svSCDIPIsyt1I5xvDIEe3OMdclSjNUItqSCCsu3q gRGnc4v5b/rf7m35BqCYCgq+BzaA134BVaOGyzXHJtNJeJHTccsAhtySMSfbXp2LVY l8Lvwdcq9R5Hw== Date: Fri, 7 Jan 2022 13:53:34 +0200 From: Jarkko Sakkinen To: Dave Hansen Cc: linux-kernel@vger.kernel.org, patches@lists.linux.dev, nathan@kernel.org, gregkh@linuxfoundation.org, linux-sgx@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH] [v3] x86/sgx: Fix NULL pointer dereference on non-SGX systems Message-ID: References: <20220104171527.5E8416A8@davehans-spike.ostc.intel.com> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jan 07, 2022 at 01:47:00PM +0200, Jarkko Sakkinen wrote: > On Tue, Jan 04, 2022 at 09:15:27AM -0800, Dave Hansen wrote: > > > > From: Dave Hansen > > > > == 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 > > Signed-off-by: Dave Hansen > > CC: Greg Kroah-Hartman > > Cc: Jarkko Sakkinen > > 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(-) > > > > 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 > > #include > > #include > > +#include > > #include > > #include > > #include > > #include > > #include > > +#include > > #include > > #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; > > _ > > Please add both: > > Reviewed-by: Jarkko Sakkinen > Tested-by: Jarkko Sakkinen > > I explained the testing procedure in the other email. To add: I tested both this final version and also the earlier attached version. /Jarkko