Re: [PATCH] analyzer: fix ICE casued by dup2 in sm-fd.cc[PR106551]

[David Malcolm <dmalcolm@redhat.com>]

On Wed, 2022-08-10 at 20:34 +0530, Mir Immad wrote:
>  > if you convert the "int m;" locals into an extern global, like in
> > comment #0 of bug 106551, does that still trigger the crash on the
> > unpatched sm-fd.cc?
> 
> Yes, it does, since m would be in "m_start" state. I'm sending an
> updated
> patch.

Great!  

Note that I recently committed a fix for bug 106573, which has an xfail
on a dg-bogus to mark a false positive which your patch hopefully also
fixes (in fd-uninit-1.c).  Can you please rebase and see if your patch
does fix it?

Thanks
Dave


> 
> Thanks
> Immad.
> 
> On Wed, Aug 10, 2022 at 1:32 AM David Malcolm <dmalcolm@redhat.com>
> wrote:
> 
> > On Tue, 2022-08-09 at 21:42 +0530, Immad Mir wrote:
> > > This patch fixes the ICE caused by valid_to_unchecked_state,
> > > at analyzer/sm-fd.cc by handling the m_start state in
> > > check_for_dup.
> > > 
> > > Tested lightly on x86_64.
> > > 
> > > gcc/analyzer/ChangeLog:
> > >         PR analyzer/106551
> > >         * sm-fd.cc (check_for_dup): handle the m_start
> > >         state when transitioning the state of LHS
> > >         of dup, dup2 and dup3 call.
> > > 
> > > gcc/testsuite/ChangeLog:
> > >         * gcc.dg/analyzer/fd-dup-1.c: New testcases.
> > > 
> > > Signed-off-by: Immad Mir <mirimmad@outlook.com>
> > > ---
> > >  gcc/analyzer/sm-fd.cc                    |  4 ++--
> > >  gcc/testsuite/gcc.dg/analyzer/fd-dup-1.c | 28
> > > +++++++++++++++++++++++-
> > >  2 files changed, 29 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/gcc/analyzer/sm-fd.cc b/gcc/analyzer/sm-fd.cc
> > > index 8bb76d72b05..c8b9930a7b6 100644
> > > --- a/gcc/analyzer/sm-fd.cc
> > > +++ b/gcc/analyzer/sm-fd.cc
> > > @@ -983,7 +983,7 @@ fd_state_machine::check_for_dup (sm_context
> > > *sm_ctxt, const supernode *node,
> > >      case DUP_1:
> > >        if (lhs)
> > >         {
> > > -         if (is_constant_fd_p (state_arg_1))
> > > +         if (is_constant_fd_p (state_arg_1) || state_arg_1 ==
> > > m_start)
> > >             sm_ctxt->set_next_state (stmt, lhs,
> > > m_unchecked_read_write);
> > >           else
> > >             sm_ctxt->set_next_state (stmt, lhs,
> > > @@ -1011,7 +1011,7 @@ fd_state_machine::check_for_dup (sm_context
> > > *sm_ctxt, const supernode *node,
> > >        file descriptor i.e the first argument.  */
> > >        if (lhs)
> > >         {
> > > -         if (is_constant_fd_p (state_arg_1))
> > > +         if (is_constant_fd_p (state_arg_1) || state_arg_1 ==
> > > m_start)
> > >             sm_ctxt->set_next_state (stmt, lhs,
> > > m_unchecked_read_write);
> > >           else
> > >             sm_ctxt->set_next_state (stmt, lhs,
> > > diff --git a/gcc/testsuite/gcc.dg/analyzer/fd-dup-1.c
> > > b/gcc/testsuite/gcc.dg/analyzer/fd-dup-1.c
> > > index eba2570568f..ed4d6de57db 100644
> > > --- a/gcc/testsuite/gcc.dg/analyzer/fd-dup-1.c
> > > +++ b/gcc/testsuite/gcc.dg/analyzer/fd-dup-1.c
> > > @@ -220,4 +220,30 @@ test_19 (const char *path, void *buf)
> > >          close (fd);
> > >      }
> > > 
> > > -}
> > > \ No newline at end of file
> > > +}
> > > +
> > > +void
> > > +test_20 ()
> > > +{
> > > +    int m;
> > > +    int fd = dup (m); /* { dg-warning "'dup' on possibly invalid
> > > file descriptor 'm'" } */
> > > +    close (fd);
> > > +}
> > > +
> > > +void
> > > +test_21 ()
> > > +{
> > > +    int m;
> > > +    int fd = dup2 (m, 1); /* { dg-warning "'dup2' on possibly
> > > invalid file descriptor 'm'" } */
> > > +    close (fd);
> > > +}
> > > +
> > > +void
> > > +test_22 (int flags)
> > > +{
> > > +    int m;
> > > +    int fd = dup3 (m, 1, flags); /* { dg-warning "'dup3' on
> > > possibly
> > > invalid file descriptor 'm'" } */
> > > +    close (fd);
> > > +}
> > 
> > Thanks for the updated patch.
> > 
> > The test cases looked suspicious to me - I was wondering why the
> > analyzer doesn't complain about the uninitialized values being
> > passed
> > to the various dup functions as parameters.  So your test cases
> > seem to
> > have uncovered a hidden pre-existing bug in the analyzer's
> > uninitialized value detection, which I've filed for myself to deal
> > with
> > as PR analyzer/106573.
> > 
> > If you convert the "int m;" locals into an extern global, like in
> > comment #0 of bug 106551, does that still trigger the crash on the
> > unpatched sm-fd.cc?  If so, then that's greatly preferable as a
> > regression test, since otherwise I'll have to modify that test case
> > when I fix bug 106573.
> > 
> > Dave
> > 
> > 
> > 
> >