Commit da99075c authored by Jan Beulich's avatar Jan Beulich Committed by Linus Torvalds

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: default avatarJan Beulich <jbeulich@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 214f766e
......@@ -2017,7 +2017,7 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
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 *fmt, va_list args)
* 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 *fmt, va_list args)
}
}
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 *fmt, va_list args)
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 *fmt, va_list args)
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);
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment