lib: vsprintf: scanf: Negative number must have field width > 1

If a signed number field starts with a '-' the field width must be > 1,
or unlimited, to allow at least one digit after the '-'.

This patch adds a check for this. If a signed field starts with '-'
and field_width == 1 the scanf will quit.

It is ok for a signed number field to have a field width of 1 if it
starts with a digit. In that case the single digit can be converted.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210514161206.30821-1-rf@opensource.cirrus.com

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 6c56c62..af30758 100644 (file)
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -3526,8 +3526,12 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
                str = skip_spaces(str);
 
                digit = *str;
-               if (is_sign && digit == '-')
+               if (is_sign && digit == '-') {
+                       if (field_width == 1)
+                               break;
+
                        digit = *(str + 1);
+               }
 
                if (!digit
                    || (base == 16 && !isxdigit(digit))