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 <jbeul...@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
---
lib/vsprintf.c | 33 ++++++++++++++-------------------
1 file changed, 14 insertions(+), 19 deletions(-)
--- 3.6-rc6/lib/vsprintf.c
+++ 3.6-rc6-sscanf-conformance/lib/vsprintf.c
@@ -2017,7 +2017,7 @@ int vsscanf(const char *buf, const char
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 @@ int vsscanf(const char *buf, const char
* 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 @@ int vsscanf(const char *buf, const char
}
}
- 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 @@ int vsscanf(const char *buf, const char
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 @@ int vsscanf(const char *buf, const char
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);
--
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