[Patch v3 Part2 2/9] x86/microcode: Report invalid writes to reload sysfs file

[Ashok Raj]

Semantics of the microcode reload file are only defined if a "1" is
written. But the code silently treats any other unsigned integer as a
successful write even though no actions are performed to load microcode.

Report those erroneous writes back to user.

Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>
Cc: x86 <x86@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Alison Schofield <alison.schofield@xxxxxxxxx>
Cc: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Cc: Thomas Gleixner (Intel) <tglx@xxxxxxxxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: Stefan Talpalaru <stefantalpalaru@xxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Rafael J. Wysocki <rafael@xxxxxxxxxx>
Cc: Peter Zilstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Martin Pohlack <mpohlack@xxxxxxxxx>
---
 arch/x86/kernel/cpu/microcode/core.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 1c6831b8b244..e4b4dfcf2d18 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -476,11 +476,8 @@ static ssize_t reload_store(struct device *dev,
 	ssize_t ret;
 
 	ret = kstrtoul(buf, 0, &val);
-	if (ret)
-		return ret;
-
-	if (val != 1)
-		return size;
+	if (ret || val != 1)
+		return -EINVAL;
 
 	cpus_read_lock();
 
-- 
2.37.2