[valgrind] [Bug 472219] Syscall param ppoll(ufds.events) points to uninitialised byte(s)

[Paul Floyd]

https://bugs.kde.org/show_bug.cgi?id=472219

--- Comment #4 from Paul Floyd <pjfl...@wanadoo.fr> ---
This does look like a Valgrind bug:

The manpage says

The field fd contains a file descriptor for an open file. If this field is
negative, then the corresponding events field is ignored and the revents field
returns zero. (This provides an easy way of ignoring a file descriptor for a
single poll() call: simply negate the fd field.) 

But we don't check for that:

   for (i = 0; i < ARG2; i++) {
      PRE_MEM_READ( "ppoll(ufds.fd)",
                    (Addr)(&ufds[i].fd), sizeof(ufds[i].fd) );
      PRE_MEM_READ( "ppoll(ufds.events)",
                    (Addr)(&ufds[i].events), sizeof(ufds[i].events) );
      PRE_MEM_WRITE( "ppoll(ufds.revents)",
                     (Addr)(&ufds[i].revents), sizeof(ufds[i].revents) );
   }

I think that should be

   for (i = 0; i < ARG2; i++) {
      PRE_MEM_READ( "ppoll(ufds.fd)",
                    (Addr)(&ufds[i].fd), sizeof(ufds[i].fd) );
      if (ufds[i].fd >= 0) { 
         PRE_MEM_READ( "ppoll(ufds.events)",
                       (Addr)(&ufds[i].events), sizeof(ufds[i].events) );
      }
      PRE_MEM_WRITE( "ppoll(ufds.revents)",
                     (Addr)(&ufds[i].revents), sizeof(ufds[i].revents) );
   }

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