[PATCH 3/4] Add strict version of vsscanf()

[Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>]

Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
---
 include/linux/kernel.h |  4 ++++
 lib/vsprintf.c         | 43 +++++++++++++++++++++++++++++++++++++++---
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 
0d91e0af01250c1d82f4a2ea562d2619b9cc6e9c..b348b84ce9c4e95031f67e0cbac5de8deca69aac
 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -227,8 +227,12 @@ const char *kvasprintf_const(gfp_t gfp, const char *fmt, 
va_list args);
 
 extern __scanf(2, 3)
 int sscanf(const char *, const char *, ...);
+extern __scanf(2, 3)
+int sscanf_strict(const char *, const char *, ...);
 extern __scanf(2, 0)
 int vsscanf(const char *, const char *, va_list);
+extern __scanf(2, 0)
+int vsscanf_strict(const char *, const char *, va_list);
 
 extern int no_hash_pointers_enable(char *str);
 
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 
9846d2385f5b9e8f3945a5664d81047e97cf10d5..2dae357b367e1da8b1004ed6e85e051a045ca36b
 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -3414,6 +3414,8 @@ EXPORT_SYMBOL_GPL(bprintf);
 
 #endif /* CONFIG_BINARY_PRINTF */
 
+static int vsscanf_internal(const char *buf, const char *fmt, va_list args, 
bool strict);
+
 /**
  * vsscanf - Unformat a buffer into a list of arguments
  * @buf:       input buffer
@@ -3421,6 +3423,23 @@ EXPORT_SYMBOL_GPL(bprintf);
  * @args:      arguments
  */
 int vsscanf(const char *buf, const char *fmt, va_list args)
+{
+       return vsscanf_internal(buf, fmt, args, false);
+}
+
+/**
+ * vsscanf_strict - Unformat a buffer into a list of arguments, but
+ *                  do not skip spaces.
+ * @buf:       input buffer
+ * @fmt:       format of buffer
+ * @args:      arguments
+ */
+int vsscanf_strict(const char *buf, const char *fmt, va_list args)
+{
+       return vsscanf_internal(buf, fmt, args, true);
+}
+
+static int vsscanf_internal(const char *buf, const char *fmt, va_list args, 
bool strict)
 {
        const char *str = buf;
        char *next;
@@ -3530,8 +3549,10 @@ int vsscanf(const char *buf, const char *fmt, va_list 
args)
                        char *s = (char *)va_arg(args, char *);
                        if (field_width == -1)
                                field_width = SHRT_MAX;
-                       /* first, skip leading white space in buffer */
-                       str = skip_spaces(str);
+                       if (!strict) {
+                               /* first, skip leading white space in buffer */
+                               str = skip_spaces(str);
+                       }
 
                        /* now copy until next white space */
                        while (*str && !isspace(*str) && field_width--)
@@ -3621,7 +3642,8 @@ int vsscanf(const char *buf, const char *fmt, va_list 
args)
                /* have some sort of integer conversion.
                 * first, skip white space in buffer.
                 */
-               str = skip_spaces(str);
+               if (!strict)
+                       str = skip_spaces(str);
 
                digit = *str;
                if (is_sign && digit == '-') {
@@ -3721,6 +3743,9 @@ int vsscanf(const char *buf, const char *fmt, va_list 
args)
                str = next;
        }
 
+       if (strict && *str)
+               return -EINVAL;
+
        return num;
 }
 EXPORT_SYMBOL(vsscanf);
@@ -3743,3 +3768,15 @@ int sscanf(const char *buf, const char *fmt, ...)
        return i;
 }
 EXPORT_SYMBOL(sscanf);
+int sscanf_strict(const char *buf, const char *fmt, ...)
+{
+       va_list args;
+       int i;
+
+       va_start(args, fmt);
+       i = vsscanf_strict(buf, fmt, args);
+       va_end(args);
+
+       return i;
+}
+EXPORT_SYMBOL(sscanf_strict);
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab