x86/intel_rdt: Fix a silent failure when writing zero value schemata
authorXiaochen Shen <xiaochen.shen@intel.com>
Fri, 10 Nov 2017 19:16:24 +0000 (11:16 -0800)
committerThomas Gleixner <tglx@linutronix.de>
Sun, 12 Nov 2017 08:01:40 +0000 (09:01 +0100)
commit2244645ab194fe45ffcbaa08f235c8f0c7fb54fc
treebc04fef616b292f1e3c31d43d75dcb307bf197b1
parent87943db7dfb0c5ee5aa74a9ac06346fadd9695c8
x86/intel_rdt: Fix a silent failure when writing zero value schemata

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: c4026b7b95a4 ("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
arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c