lib/vsprintf.c: improve standard conformance of sscanf() (da99075c) · Commits · 戴 / test

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>

lib/vsprintf.c

+14 −19

Original line number	Diff line number	Diff line
		@@ -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);

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