lib/vsprintf.c: improve standard conformance of sscanf()
Xen's pciback points out a couple of deficiencies with vsscanf()'s
standard conformance:
- Trailing character matching cannot be checked by the caller: With a
format string of "(%x:%x.%x) %n" absence of the closing parenthesis
cannot be checked, as input of "(00:00.0)" doesn't cause the %n to be
evaluated (because of the code not skipping white space before the
trailing %n).
- The parameter corresponding to a trailing %n could get filled even if
there was a matching error: With a format string of "(%x:%x.%x)%n",
input of "(00:00.0]" would still fill the respective variable pointed to
(and hence again make the mismatch non-detectable by the caller).
This patch aims at fixing those, but leaves other non-conforming aspects
of it untouched, among them these possibly relevant ones:
- improper handling of the assignment suppression character '*' (blindly
discarding all succeeding non-white space from the format and input
strings),
- not honoring conversion specifiers for %n, - not recognizing the C99
conversion specifier 't' (recognized by vsprintf()).
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 9287e25..39c99fe 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2017,7 +2017,7 @@
s16 field_width;
bool is_sign;
- while (*fmt && *str) {
+ while (*fmt) {
/* skip any white space in format */
/* white space in format matchs any amount of
* white space, including none, in the input.
@@ -2042,6 +2042,8 @@
* advance both strings to next white space
*/
if (*fmt == '*') {
+ if (!*str)
+ break;
while (!isspace(*fmt) && *fmt != '%' && *fmt)
fmt++;
while (!isspace(*str) && *str)
@@ -2070,7 +2072,17 @@
}
}
- if (!*fmt || !*str)
+ if (!*fmt)
+ break;
+
+ if (*fmt == 'n') {
+ /* return number of characters read so far */
+ *va_arg(args, int *) = str - buf;
+ ++fmt;
+ continue;
+ }
+
+ if (!*str)
break;
base = 10;
@@ -2103,13 +2115,6 @@
num++;
}
continue;
- case 'n':
- /* return number of characters read so far */
- {
- int *i = (int *)va_arg(args, int*);
- *i = str - buf;
- }
- continue;
case 'o':
base = 8;
break;
@@ -2210,16 +2215,6 @@
str = next;
}
- /*
- * Now we've come all the way through so either the input string or the
- * format ended. In the former case, there can be a %n at the current
- * position in the format that needs to be filled.
- */
- if (*fmt == '%' && *(fmt + 1) == 'n') {
- int *p = (int *)va_arg(args, int *);
- *p = str - buf;
- }
-
return num;
}
EXPORT_SYMBOL(vsscanf);