[PATCH v8 1/4] lib: vsprintf: scanf: Negative number must have field width > 1

Richard Fitzgerald
2021-03-30T10:47:57Z

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>
---
lib/vsprintf.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 41ddc353ebb8..f78651e9b030 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -3466,8 +3466,12 @@ 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))
--
2.20.1