From c5e82091bf8b4a344cf48bb4c6a8597033ab50c2 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 21 Sep 2012 11:02:10 +1000 Subject: [PATCH] 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 Cc: Konrad Rzeszutek Wilk Signed-off-by: Andrew Morton --- lib/vsprintf.c | 33 ++++++++++++++------------------- 1 file changed, 14 insertions(+), 19 deletions(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index d4cce101083c..6a09556e3f37 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2019,7 +2019,7 @@ 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. @@ -2044,6 +2044,8 @@ 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) @@ -2072,7 +2074,17 @@ 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; @@ -2105,13 +2117,6 @@ 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; @@ -2212,16 +2217,6 @@ 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); -- 2.39.5