On 27 January 2017 at 04:18, Qiuping Yi <yiqiup...@gmail.com> wrote: > Dear all, > > I encountered a strange problem when testing the next code snippet: > > 1 if (pw = getpwuid(getuid()) == NULL) > 2 return ; > > 3 .. = pw->pw_dir;
Please use the correct mailing list (klee-dev@imperial.ac.uk) instead of the old klee-...@keeda.stanford.edu mailing list. It would be better if you provided a small complete example. Like this. ``` #include <assert.h> #include <pwd.h> #include <sys/types.h> #include <stdio.h> #include <unistd.h> int main(int arc, char** argv) { struct passwd* pw; uid_t uid = getuid(); printf("uid is %d\n", uid); if (pw = getpwuid(getuid()) == NULL) { printf("Failed\n"); return 1; } assert(pw && "pw cannot be NULL"); char* pw_dir = pw->pw_dir; printf("pw_dir: %s\n", pw_dir); return 0; } ``` Your code is wrong. if (pw = getpwuid(getuid()) == NULL) is doing this if ( pw = ( getpwuid(getuid()) == NULL ) so a pointer is returned by `getpwuid()` and then we compare with NULL which is false so then `pw` gets assigned the value zero. However once I fix your code to if ((pw = getpwuid(getuid())) == NULL) { then I can reproduce the problem if I just run `klee program.bc` I suspect it's to do with the fact `getpwuid()` returns a pointer to "real memory" which does not point to anything in KLEE's own model of the memory (i.e. the address space of the program under). To fix this you need not call `getpwuid()` as an external function but instead call it from klee-uclibc so that it can be symbolically executed. If you run ``` klee -libc=uclibc program.bc ``` no out of bounds access is reported. HTH, Dan. _______________________________________________ klee-dev mailing list klee-dev@imperial.ac.uk https://mailman.ic.ac.uk/mailman/listinfo/klee-dev