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SubjectRe: [PATCH 3/3] x86/intel_rdt: Return error for incorrect resource names in schemata
On Wed, 19 Apr 2017, Vikas Shivappa wrote:

> When schemata parses the resource names, currently it may not return
> error for incorrect resource names and fail quietly without updating the
> control values.
>
> This is because for_each_enabled_rdt_resource(r) leaves "r" pointing
> beyond the end of the rdt_resources_all[] array, and we check for
> !r->name which results in an out of bounds access and also may not be
> NULL, hence we may not detect that we did not find the name user
> supplied.
>
> Update this to check (r == (rdt_resources_all + RDT_NUM_RESOURCES))
> instead.
>
> Reported-by: Prakhya, Sai Praneeth <sai.praneeth.prakhya@intel.com>
> Signed-off-by: Vikas Shivappa <vikas.shivappa@linux.intel.com>
> Tested-by: Prakhya, Sai Praneeth <sai.praneeth.prakhya@intel.com>
> ---
> arch/x86/kernel/cpu/intel_rdt_schemata.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/intel_rdt_schemata.c b/arch/x86/kernel/cpu/intel_rdt_schemata.c
> index 3cfa1ca..bb99bd8 100644
> --- a/arch/x86/kernel/cpu/intel_rdt_schemata.c
> +++ b/arch/x86/kernel/cpu/intel_rdt_schemata.c
> @@ -228,7 +228,7 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
> break;
> }
> }
> - if (!r->name) {
> + if (r == (rdt_resources_all + RDT_NUM_RESOURCES)) {
> ret = -EINVAL;
> goto out;
> }

The resulting loop is just horrible to read. We can do better than
that. Patch below.

Thanks,

tglx
8<-------------

--- a/arch/x86/kernel/cpu/intel_rdt_schemata.c
+++ b/arch/x86/kernel/cpu/intel_rdt_schemata.c
@@ -187,6 +187,17 @@ static int update_domains(struct rdt_res
return 0;
}

+static int rdtgroup_parse_resource(char *resname, char *tok, int closid)
+{
+ struct rdt_resource *r;
+
+ for_each_enabled_rdt_resource(r) {
+ if (!strcmp(resname, r->name) && closid < r->num_closid)
+ return parse_line(tok, r);
+ }
+ return -EINVAL;
+}
+
ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
@@ -209,9 +220,10 @@ ssize_t rdtgroup_schemata_write(struct k

closid = rdtgrp->closid;

- for_each_enabled_rdt_resource(r)
+ for_each_enabled_rdt_resource(r) {
list_for_each_entry(dom, &r->domains, list)
dom->have_new_ctrl = false;
+ }

while ((tok = strsep(&buf, "\n")) != NULL) {
resname = strsep(&tok, ":");
@@ -219,19 +231,9 @@ ssize_t rdtgroup_schemata_write(struct k
ret = -EINVAL;
goto out;
}
- for_each_enabled_rdt_resource(r) {
- if (!strcmp(strim(resname), r->name) &&
- closid < r->num_closid) {
- ret = parse_line(tok, r);
- if (ret)
- goto out;
- break;
- }
- }
- if (!r->name) {
- ret = -EINVAL;
+ ret = rdtgroup_parse_resource(strim(resname), tok, closid);
+ if (ret)
goto out;
- }
}

for_each_enabled_rdt_resource(r) {
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