On Tue, Feb 23, 2016 at 12:38 PM, Jessica Yu <[email protected]> wrote: > Implement basic character sets for the '%[]' conversion specifier. > > The '%[]' conversion specifier matches a nonempty sequence of characters > from the specified set of accepted (or with '^', rejected) characters > between the brackets. The substring matched is to be made up of characters > in (or not in) the set. This implementation differs from its glibc > counterpart in that it does not support character ranges (e.g., 'a-z' or > '0-9'), the hyphen '-' is *not* a special character, and the brackets > themselves cannot be matched. > > Signed-off-by: Jessica Yu <[email protected]>
Reviewed-by: Kees Cook <[email protected]> -Kees > --- > > This patch adds support for the '%[' conversion specifier for sscanf(). > This is useful in cases where we'd like to match substrings delimited by > something other than spaces. The original motivation for this patch > actually came from a livepatch discussion (See: > https://lkml.org/lkml/2016/2/8/790), > where we were trying to come up with a clean way to parse symbol names with > substrings delimited by periods and commas. > > Patch based on linux-next-20160223. > > v3: > - Fix memory leak in error path (kfree() before returning) > - Remove redundant condition in while loop > - Style fix (*op)() -> op() > > v2: > - Use kstrndup() to copy the character set from fmt instead of using a > statically allocated array > > lib/vsprintf.c | 41 +++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 41 insertions(+) > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index 525c8e1..983358a 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -2714,6 +2714,47 @@ int vsscanf(const char *buf, const char *fmt, va_list > args) > num++; > } > continue; > + case '[': > + { > + char *s = (char *)va_arg(args, char *); > + char *set; > + size_t (*op)(const char *str, const char *set); > + size_t len = 0; > + bool negate = (*(fmt) == '^'); > + > + if (field_width == -1) > + field_width = SHRT_MAX; > + > + op = negate ? &strcspn : &strspn; > + if (negate) > + fmt++; > + > + len = strcspn(fmt, "]"); > + /* invalid format; stop here */ > + if (!len) > + return num; > + > + set = kstrndup(fmt, len, GFP_KERNEL); > + if (!set) > + return num; > + > + /* advance fmt past ']' */ > + fmt += len + 1; > + > + len = op(str, set); > + /* no matches */ > + if (!len) { > + kfree(set); > + return num; > + } > + > + while (len-- && field_width--) > + *s++ = *str++; > + *s = '\0'; > + kfree(set); > + num++; > + } > + continue; > case 'o': > base = 8; > break; > -- > 2.4.3 > -- Kees Cook Chrome OS & Brillo Security
