linux-kernel - [PATCH v2 2/2] misc: amd-sbi: Address copy_to/from

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Message-ID: <20250625110707.315489-2-akshay.gupta@amd.com>
Date: Wed, 25 Jun 2025 11:07:07 +0000
From: Akshay Gupta <akshay.gupta@....com>
To: <linux-kernel@...r.kernel.org>
CC: <gregkh@...uxfoundation.org>, <arnd@...db.de>, <shyam-sundar.s-k@....com>,
	<gautham.shenoy@....com>, <mario.limonciello@....com>,
	<naveenkrishna.chatradhi@....com>, <anand.umarji@....com>, Akshay Gupta
	<akshay.gupta@....com>, Dan Carpenter <dan.carpenter@...aro.org>
Subject: [PATCH v2 2/2] misc: amd-sbi: Address copy_to/from_user() warning reported in smatch

Smatch warnings are reported for below commit,

Commit bb13a84ed6b7 ("misc: amd-sbi: Add support for CPUID protocol")
from Apr 28, 2025 (linux-next), leads to the following Smatch static
checker warning:

drivers/misc/amd-sbi/rmi-core.c:376 apml_rmi_reg_xfer() warn: maybe return -EFAULT instead of the bytes remaining?
drivers/misc/amd-sbi/rmi-core.c:394 apml_mailbox_xfer() warn: maybe return -EFAULT instead of the bytes remaining?
drivers/misc/amd-sbi/rmi-core.c:411 apml_cpuid_xfer() warn: maybe return -EFAULT instead of the bytes remaining?
drivers/misc/amd-sbi/rmi-core.c:428 apml_mcamsr_xfer() warn: maybe return -EFAULT instead of the bytes remaining?

copy_to/from_user() returns number of bytes, not copied.
In case data not copied, return "-EFAULT".

Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
Closes: https://lore.kernel.org/all/aDVyO8ByVsceybk9@stanley.mountain/
Reviewed-by: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@....com>
Signed-off-by: Akshay Gupta <akshay.gupta@....com>
---
Changes from v1:
 - Split patch as per Greg's suggestion
 drivers/misc/amd-sbi/rmi-core.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/amd-sbi/rmi-core.c b/drivers/misc/amd-sbi/rmi-core.c
index 3570f3b269a9..9048517c088c 100644
--- a/drivers/misc/amd-sbi/rmi-core.c
+++ b/drivers/misc/amd-sbi/rmi-core.c
@@ -372,7 +372,8 @@ static int apml_rmi_reg_xfer(struct sbrmi_data *data,
 	mutex_unlock(&data->lock);
 
 	if (msg.rflag && !ret)
-		return copy_to_user(arg, &msg, sizeof(struct apml_reg_xfer_msg));
+		if (copy_to_user(arg, &msg, sizeof(struct apml_reg_xfer_msg)))
+			return -EFAULT;
 	return ret;
 }
 
@@ -390,7 +391,9 @@ static int apml_mailbox_xfer(struct sbrmi_data *data, struct apml_mbox_msg __use
 	if (ret && ret != -EPROTOTYPE)
 		return ret;
 
-	return copy_to_user(arg, &msg, sizeof(struct apml_mbox_msg));
+	if (copy_to_user(arg, &msg, sizeof(struct apml_mbox_msg)))
+		return -EFAULT;
+	return ret;
 }
 
 static int apml_cpuid_xfer(struct sbrmi_data *data, struct apml_cpuid_msg __user *arg)
@@ -407,7 +410,9 @@ static int apml_cpuid_xfer(struct sbrmi_data *data, struct apml_cpuid_msg __user
 	if (ret && ret != -EPROTOTYPE)
 		return ret;
 
-	return copy_to_user(arg, &msg, sizeof(struct apml_cpuid_msg));
+	if (copy_to_user(arg, &msg, sizeof(struct apml_cpuid_msg)))
+		return -EFAULT;
+	return ret;
 }
 
 static int apml_mcamsr_xfer(struct sbrmi_data *data, struct apml_mcamsr_msg __user *arg)
@@ -424,7 +429,9 @@ static int apml_mcamsr_xfer(struct sbrmi_data *data, struct apml_mcamsr_msg __us
 	if (ret && ret != -EPROTOTYPE)
 		return ret;
 
-	return copy_to_user(arg, &msg, sizeof(struct apml_mcamsr_msg));
+	if (copy_to_user(arg, &msg, sizeof(struct apml_mcamsr_msg)))
+		return -EFAULT;
+	return ret;
 }
 
 static long sbrmi_ioctl(struct file *fp, unsigned int cmd, unsigned long arg)
-- 
2.25.1