[uclibc-ng-devel] Issue: Possible buffer overflow in _vfprintf.c (out-of-bounds access)

Dear uclibc-ng developers, We have run a static analysis tool (Klocwork) in uclibc and one of its checkers (ABV.GENERAL) indicates a potential buffer overflow in uclibc-ng/src/master/libc/stdio/_vfprintf.c:1045 The problem occurs as an out-of-bounds access to array 'argtype', which is a member of 'ppfs_t'. This array has length 'MAX_ARGS'. According to the static analysis tool, the array can be accessed using index 'n' of value '-1' and '9..254' in the conditional shown below: // File: uclibc-ng/src/master/libc/stdio/_vfprintf.c:1045   if (_is_equal_or_bigger_arg(ppfs->argtype[n], argtype[i])) {     ppfs->argtype[n] = argtype[i];   } Triggering an out-of-bounds access for 'n=-1' is relatively simply when using printf or similar functions (e.g. vfprintf). Such out-of-bounds access occurs when positional arguments are specified, as in the following statement:   printf("%1$s", "Hello world!"); Although Klocwork claims that the array might be accessed using indexes '9..254', we were not able to trigger an out-of-bounds access for indexes in this range. Kind regards, Diego Dias -- Diego M. Dias, Systems Verification Engineer at Kernkonzept, diego.dias(a)kernkonzept.com Phone: +49 351 41883231 Kernkonzept GmbH at Dresden, Germany, HRB 31129, CEO Dr.-Ing. Michael Hohmuth