x86: msr: correct return value on partial operations

Return the correct return value when the MSR driver partially
completes a request (we should return the number of bytes actually
read or written, instead of the error code.)

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 18 insertions, 10 deletions

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 9c34a1005dba..2e2af5d18191 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -72,7 +72,8 @@ static ssize_t msr_read(struct file *file, char __user *buf,
         u32 data[2];
         u32 reg = *ppos;
         int cpu = iminor(file->f_path.dentry->d_inode);
-        int err;
+        int err = 0;
+        ssize_t bytes = 0;
 
         if (count % 8)
                 return -EINVAL; /* Invalid chunk size */
@@ -82,14 +83,17 @@ static ssize_t msr_read(struct file *file, char __user *buf,
                 if (err) {
                         if (err == -EFAULT) /* Fix idiotic error code */
                                 err = -EIO;
-                        return err;
+                        break;
+                }
+                if (copy_to_user(tmp, &data, 8)) {
+                        err = -EFAULT;
+                        break;
                 }
-                if (copy_to_user(tmp, &data, 8))
-                        return -EFAULT;
                 tmp += 2;
+                bytes += 8;
         }
 
-        return ((char __user *)tmp) - buf;
+        return bytes ? bytes : err;
 }
 
 static ssize_t msr_write(struct file *file, const char __user *buf,
@@ -99,24 +103,28 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
         u32 data[2];
         u32 reg = *ppos;
         int cpu = iminor(file->f_path.dentry->d_inode);
-        int err;
+        int err = 0;
+        ssize_t bytes = 0;
 
         if (count % 8)
                 return -EINVAL; /* Invalid chunk size */
 
         for (; count; count -= 8) {
-                if (copy_from_user(&data, tmp, 8))
-                        return -EFAULT;
+                if (copy_from_user(&data, tmp, 8)) {
+                        err = -EFAULT;
+                        break;
+                }
                 err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
                 if (err) {
                         if (err == -EFAULT) /* Fix idiotic error code */
                                 err = -EIO;
-                        return err;
+                        break;
                 }
                 tmp += 2;
+                bytes += 8;
         }
 
-        return ((char __user *)tmp) - buf;
+        return bytes ? bytes : err;
 }
 
 static int msr_open(struct inode *inode, struct file *file)