x86: cpuid: correct return value on partial operations

Return the correct return value when the CPUID 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, 9 insertions, 5 deletions

diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
index 23e8316c8357..8e9cd6a8ec12 100644
--- a/arch/x86/kernel/cpuid.c
+++ b/arch/x86/kernel/cpuid.c
@@ -89,7 +89,8 @@ static ssize_t cpuid_read(struct file *file, char __user *buf,
         struct cpuid_regs cmd;
         int cpu = iminor(file->f_path.dentry->d_inode);
         u64 pos = *ppos;
-        int err;
+        ssize_t bytes = 0;
+        int err = 0;
 
         if (count % 16)
                 return -EINVAL; /* Invalid chunk size */
@@ -99,14 +100,17 @@ static ssize_t cpuid_read(struct file *file, char __user *buf,
                 cmd.ecx = pos >> 32;
                 err = smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1);
                 if (err)
-                        return err;
-                if (copy_to_user(tmp, &cmd, 16))
-                        return -EFAULT;
+                        break;
+                if (copy_to_user(tmp, &cmd, 16)) {
+                        err = -EFAULT;
+                        break;
+                }
                 tmp += 16;
+                bytes += 16;
                 *ppos = ++pos;
         }
 
-        return tmp - buf;
+        return bytes ? bytes : err;
 }
 
 static int cpuid_open(struct inode *inode, struct file *file)