[tip: x86/microcode] x86/microcode: Allow only "1" as a late reload trigger value

[tip-bot2 for Ashok Raj]

The following commit has been merged into the x86/microcode branch of tip:

Commit-ID:     25d0dc4b957cc8674f8554e85f18a00467e876d7
Gitweb:        https://git.kernel.org/tip/25d0dc4b957cc8674f8554e85f18a00467e876d7
Author:        Ashok Raj <ashok.raj@xxxxxxxxx>
AuthorDate:    Mon, 30 Jan 2023 13:39:48 -08:00
Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Tue, 31 Jan 2023 16:47:03 +01:00

x86/microcode: Allow only "1" as a late reload trigger value

Microcode gets reloaded late only if "1" is written to the reload file.
However, the code silently treats any other unsigned integer as a
successful write even though no actions are performed to load microcode.

Make the loader more strict to accept only "1" as a trigger value and
return an error otherwise.

  [ bp: Massage commit message. ]

Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230130213955.6046-3-ashok.raj@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 61d57d9..fdd1e7e 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -475,11 +475,8 @@ static ssize_t reload_store(struct device *dev,
 	ssize_t ret = 0;
 
 	ret = kstrtoul(buf, 0, &val);
-	if (ret)
-		return ret;
-
-	if (val != 1)
-		return size;
+	if (ret || val != 1)
+		return -EINVAL;
 
 	cpus_read_lock();