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author | Jan Beulich <JBeulich@suse.com> | 2012-10-04 17:13:24 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-10-06 03:04:58 +0900 |
commit | da99075c1d368315e1508b6143226c0d27b621e0 (patch) | |
tree | 1ceefd8dc83bcc569640b519c00b0313be88bf1e /lib | |
parent | 214f766ea0909e743122966c4617b3a112e405d7 (diff) | |
download | lwn-da99075c1d368315e1508b6143226c0d27b621e0.tar.gz lwn-da99075c1d368315e1508b6143226c0d27b621e0.zip |
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>
Diffstat (limited to 'lib')
-rw-r--r-- | lib/vsprintf.c | 33 |
1 files changed, 14 insertions, 19 deletions
diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 9287e2549936..39c99fea7c03 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -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); |