string: Remove strncpy() from the kernel

strncpy() has been a persistent source of bugs due to its ambiguous
intended usage and frequently counter-intuitive semantics: it may not
NUL-terminate the destination, and it unconditionally zero-pads to the
full length, which isn't always needed. All former callers have been
migrated[1] to:

  - strscpy()        for NUL-terminated destinations
  - strscpy_pad()    for NUL-terminated destinations needing zero-padding
  - strtomem_pad()   for non-NUL-terminated fixed-width fields
  - memcpy_and_pad() for bounded copies with explicit padding
  - memcpy()         for known-length copies

Remove the generic implementation, its declaration, the FORTIFY_SOURCE
wrapper, and associated tests.

Link: https://github.com/KSPP/linux/issues/90 [1]
Signed-off-by: Kees Cook <kees@kernel.org>

1 files changed, 0 insertions, 16 deletions

diff --git a/lib/string.c b/lib/string.c
index b632c71df1a5..45ca1cfe0184 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -88,22 +88,6 @@ char *strcpy(char *dest, const char *src)
 EXPORT_SYMBOL(strcpy);
 #endif
 
-#ifndef __HAVE_ARCH_STRNCPY
-char *strncpy(char *dest, const char *src, size_t count)
-{
-	char *tmp = dest;
-
-	while (count) {
-		if ((*tmp = *src) != 0)
-			src++;
-		tmp++;
-		count--;
-	}
-	return dest;
-}
-EXPORT_SYMBOL(strncpy);
-#endif
-
 #ifdef __BIG_ENDIAN
 # define ALLBUTLAST_BYTE_MASK (~255ul)
 #else