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

[David Malcolm <dmalcolm@redhat.com>]

On Wed, 2022-08-10 at 22:51 +0530, Mir Immad wrote:
>  > Can you please rebase and see if your patch
> > does fix it?
> 
> No, the patch that I sent did not attempt to fix this. Now that I
> have made
> the correction, XFAIL in fd-uninit-1.c has changed to XPASS.

Great - that means that, with your fix, we no longer bogusly emit that
false positive.

> 
> Should i remove the dg-bogus warning from fd-uninit-1.c test_1?

Yes please.

Thanks
Dave

> 
> Thanks.
> Immad.
> 
> 
> On Wed, Aug 10, 2022 at 10:26 PM David Malcolm <dmalcolm@redhat.com>
> wrote:
> 
> > 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
> > > > 
> > > > 
> > > > 
> > > > 
> > 
> > 
> >