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

[Mir Immad <mirimnan017@gmail.com>]

With the fix for bogus warning in fd-uninit.c, the analyzer now does not
warning for the following code for which it would previously emit
-Wanalyzer-fd-use-without-check

extern int m;
test()
{
 int fd = dup2(m, 1);
 close(fd);
}

So I had to remove such warnings from fd-dup-1.c test_20,21,22 (in the
patch). Now these tests are only there to show fix for PR16551.

Sending an updated patch (passes style and commit checker).
Thanks.
Immad.

On Thu, Aug 11, 2022 at 12:14 AM David Malcolm <dmalcolm@redhat.com> wrote:

> 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
> > > > >
> > > > >
> > > > >
> > > > >
> > >
> > >
> > >
>
>
>