x86/mtrr: Convert to use strncpy_from_user() helper

Replace the open coded string fetch from user-space with strncpy_from_user().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Link: http://lkml.kernel.org/r/20180515180535.89703-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 2 insertions, 10 deletions

diff --git a/arch/x86/kernel/cpu/mtrr/if.c b/arch/x86/kernel/cpu/mtrr/if.c
index 42b4f2f3b557..c610f47373e4 100644
--- a/arch/x86/kernel/cpu/mtrr/if.c
+++ b/arch/x86/kernel/cpu/mtrr/if.c
@@ -106,17 +106,9 @@ mtrr_write(struct file *file, const char __user *buf, size_t len, loff_t * ppos)
 
         memset(line, 0, LINE_SIZE);
 
-        length = len;
-        length--;
-
-        if (length > LINE_SIZE - 1)
-                length = LINE_SIZE - 1;
-
+        length = strncpy_from_user(line, buf, LINE_SIZE - 1);
         if (length < 0)
-                return -EINVAL;
-
-        if (copy_from_user(line, buf, length))
-                return -EFAULT;
+                return length;
 
         linelen = strlen(line);
         ptr = line + linelen - 1;