[valgrind] [Bug 505673] Valgrind crashes with an internal error and SIGBUS when the guest tries to open its own file with O_WRONLY|O_CREAT|O_TRUNC

[Paul Floyd]

https://bugs.kde.org/show_bug.cgi?id=505673

--- Comment #18 from Paul Floyd <pjfl...@wanadoo.fr> ---
A first stab for Linux openat:

   /* And for /proc/self/exe or /proc/<pid>/exe case. */

   VG_(sprintf)(name, "/proc/%d/exe", VG_(getpid)());
   vg_assert(VG_(resolved_exename) && VG_(resolved_exename)[0] == '/');
   const HChar* path = (const HChar*)ARG2;
   if (ML_(safe_to_deref)( path, 1 )) {
      HChar tmp[VKI_PATH_MAX];
      VG_(realpath)(path, tmp);
      if (VG_(strcmp)((HChar *)(Addr)ARG2, name) == 0
           || VG_(strcmp)((HChar *)(Addr)ARG2, "/proc/self/exe") == 0
           || !VG_(strcmp)(tmp, VG_(resolved_exename))) {
         if ((ARG3 & VKI_O_WRONLY) ||
             (ARG3 & VKI_O_RDWR)) {
             SET_STATUS_Failure( VKI_ETXTBSY );
             return;
         }

         sres = VG_(dup)( VG_(cl_exec_fd) );
         SET_STATUS_from_SysRes( sres );
         if (!sr_isError(sres)) {
            OffT off = VG_(lseek)( sr_Res(sres), 0, VKI_SEEK_SET );
            if (off < 0)
               SET_STATUS_Failure( VKI_EMFILE );
         }
         return;
      }
   }

I don't like this much. We are just doing a dup of VG_(cl_exec_fd). As far as I
can see cl_exec_fd is already a dup (or 2) ultimately originating from
VG_(pre_exec_check) which does

   res = VG_(open)(exe_name, VKI_O_RDONLY, 0);

Probably mostly harmless but it does mean that we will lose any O_ flags like
O_NOATIME or O_CLOEXEC.


I think that I should make a common function for openat and openat2 for all the
flag handling.

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