x86/intel_rdt: Fix a silent failure when writing zero value schemata

xiaochenshen · KAGA-KOKO · commit 2244645ab194 · 2017-11-12T09:01:40.000+01:00
Writing an invalid schemata with no domain values (e.g., "(L3|MB):"), results in a silent failure, i.e. the last_cmd_status returns OK, Check for an empty value and set the result string with a proper error message and return -EINVAL. Before the fix: # mkdir /sys/fs/resctrl/p1 # echo "L3:" > /sys/fs/resctrl/p1/schemata (silent failure) # cat /sys/fs/resctrl/info/last_cmd_status ok # echo "MB:" > /sys/fs/resctrl/p1/schemata (silent failure) # cat /sys/fs/resctrl/info/last_cmd_status ok After the fix: # mkdir /sys/fs/resctrl/p1 # echo "L3:" > /sys/fs/resctrl/p1/schemata -bash: echo: write error: Invalid argument # cat /sys/fs/resctrl/info/last_cmd_status Missing 'L3' value # echo "MB:" > /sys/fs/resctrl/p1/schemata -bash: echo: write error: Invalid argument # cat /sys/fs/resctrl/info/last_cmd_status Missing 'MB' value [ Tony: This is an unintended side effect of the patch earlier to allow the user to just write the value they want to change. While allowing user to specify less than all of the values, it also allows an empty value. ] Fixes: c4026b7 ("x86/intel_rdt: Implement "update" mode when writing schemata file") Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com> Signed-off-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Vikas Shivappa <vikas.shivappa@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Link: https://lkml.kernel.org/r/20171110191624.20280-1-tony.luck@intel.com
diff --git a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
@@ -257,6 +257,11 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
 			ret = -EINVAL;
 			goto out;
 		}
+		if (tok[0] == '\0') {
+			rdt_last_cmd_printf("Missing '%s' value\n", resname);
+			ret = -EINVAL;
+			goto out;
+		}
 		ret = rdtgroup_parse_resource(resname, tok, closid);
 		if (ret)
 			goto out;
