From b1412a88bb616f449401be285d43b028962992b9 Mon Sep 17 00:00:00 2001

From: Arnaldo Carvalho de Melo <acme@redhat.com>

Date: Mon, 1 Jul 2019 11:37:40 -0300

Subject: [PATCH 1/1] fprintf: Fixup handling classes with no members

Will Cohen reported this NULL pointer dereference while processing some

object linking with cuda:

  #0  0x00007ffff7f91453 in __class__fprintf (class=0x522560, cu=0x40ff80, conf=0x7fffffffa930, fp=0x7ffff7ece780 <_IO_2_1_stdout_>)

      at /home/acme/git/pahole/dwarves_fprintf.c:1624

  #1  0x00007ffff7f92195 in tag__fprintf (tag=0x522560, cu=0x40ff80, conf=0x7fffffffa930, fp=0x7ffff7ece780 <_IO_2_1_stdout_>)

      at /home/acme/git/pahole/dwarves_fprintf.c:1835

  #2  0x00007ffff7f90b57 in __class__fprintf (class=0x5224c0, cu=0x40ff80, conf=0x7fffffffaaa0, fp=0x7ffff7ece780 <_IO_2_1_stdout_>)

      at /home/acme/git/pahole/dwarves_fprintf.c:1406

  #3  0x00007ffff7f92195 in tag__fprintf (tag=0x5224c0, cu=0x40ff80, conf=0x40a200 <conf>, fp=0x7ffff7ece780 <_IO_2_1_stdout_>)

      at /home/acme/git/pahole/dwarves_fprintf.c:1835

  #4  0x0000000000402d03 in class_formatter (class=0x5224c0, cu=0x40ff80, id=1257) at /home/acme/git/pahole/pahole.c:224

  #5  0x0000000000403074 in print_classes (cu=0x40ff80) at /home/acme/git/pahole/pahole.c:319

  #6  0x0000000000404bb2 in pahole_stealer (cu=0x40ff80, conf_load=0x40a240 <conf_load>) at /home/acme/git/pahole/pahole.c:1174

  #7  0x00007ffff7f9ff73 in finalize_cu (cus=0x40b2b0, cu=0x40ff80, dcu=0x7fffffffacf0, conf=0x40a240 <conf_load>)

      at /home/acme/git/pahole/dwarf_loader.c:2227

  #8  0x00007ffff7f9ffac in finalize_cu_immediately (cus=0x40b2b0, cu=0x40ff80, dcu=0x7fffffffacf0, conf=0x40a240 <conf_load>)

      at /home/acme/git/pahole/dwarf_loader.c:2236

  #9  0x00007ffff7fa064c in cus__load_module (cus=0x40b2b0, conf=0x40a240 <conf_load>, mod=0x40d760, dw=0x40e980, elf=0x40b360,

      filename=0x7fffffffd5e3 "examples/wcohen/02_Exercise.cuda") at /home/acme/git/pahole/dwarf_loader.c:2389

  #10 0x00007ffff7fa0760 in cus__process_dwflmod (dwflmod=0x40d760, userdata=0x40d770, name=0x40d910 "examples/wcohen/02_Exercise.cuda",

      base=4194304, arg=0x7fffffffcf10) at /home/acme/git/pahole/dwarf_loader.c:2434

  #11 0x00007ffff7f32be1 in dwfl_getmodules () from /lib64/libdw.so.1

  #12 0x00007ffff7fa0820 in cus__process_file (cus=0x40b2b0, conf=0x40a240 <conf_load>, fd=3,

      filename=0x7fffffffd5e3 "examples/wcohen/02_Exercise.cuda") at /home/acme/git/pahole/dwarf_loader.c:2487

  #13 0x00007ffff7fa089c in dwarf__load_file (cus=0x40b2b0, conf=0x40a240 <conf_load>, filename=0x7fffffffd5e3 "examples/wcohen/02_Exercise.cuda")

      at /home/acme/git/pahole/dwarf_loader.c:2504

  #14 0x00007ffff7f8b0dd in cus__load_file (cus=0x40b2b0, conf=0x40a240 <conf_load>, filename=0x7fffffffd5e3 "examples/wcohen/02_Exercise.cuda")

      at /home/acme/git/pahole/dwarves.c:1745

  #15 0x00007ffff7f8bc2a in cus__load_files (cus=0x40b2b0, conf=0x40a240 <conf_load>, filenames=0x7fffffffd150)

      at /home/acme/git/pahole/dwarves.c:2109

  #16 0x0000000000404ff0 in main (argc=2, argv=0x7fffffffd148) at /home/acme/git/pahole/pahole.c:1294

  (gdb)

  (gdb) p class__name(class, cu)

  $6 = 0x5cbb85 "__nv_hdl_helper_trait<__nv_dl_tag<int (*)(int, char**), main, 1u>, void (main(int, char**)::__lambda0::*)(int, double&)const>"

  (gdb) p class->type.nr_members

  $7 = 0

  (gdb) p last

  $8 = (struct class_member *) 0x0

  (gdb)

So, before checking for bitfield details, first check if there were

members.

Now, if we show all structs/classes in that object file and look for the

above data structure, we find it inside another:

  $ pahole examples/wcohen/02_Exercise.cuda

  <SNIP>

  struct __nv_hdl_helper_trait_outer<false, false, int, Kokkos::View<double**>, Kokkos::View<double*>, Kokkos::View<double*> > {

          struct __nv_hdl_helper_trait<__nv_dl_tag<int (*)(int, char**), main, 1u>, void (main(int, char**)::__lambda0::*)(int, double&)const> {

                  class __nv_hdl_wrapper_t<false, false, __nv_dl_tag<int (*)(int, char**), main, 1u>, void(int, double&), int, Kokkos::View<doubl get<main(int, char**)::__lambda0>(class __lambda0, int, class View<double**>, class View<double*>, class View<double*>);

                  /* size: 1, cachelines: 0, members: 0 */

                  /* padding: 1 */

                  /* last cacheline: 1 bytes */

          };

          /* size: 1, cachelines: 0, members: 0 */

          /* padding: 1 */

          /* last cacheline: 1 bytes */

  };

  <SNIP>

  $

Reported-by: William Cohen <wcohen@redhat.com>

Fixes: 13e5b9fc00ee ("fprintf: Add unnamed bitfield padding at the end to rebuild original type")

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

---

 dwarves_fprintf.c | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dwarves_fprintf.c b/dwarves_fprintf.c

index 8ad1ced7840c..706f1b5033f5 100644

--- a/dwarves_fprintf.c

+++ b/dwarves_fprintf.c

@@ -1620,7 +1620,7 @@ static size_t __class__fprintf(struct class *class, const struct cu *cu,

 	 * to avoid adding the forced bitfield paddings and have btfdiff happy.

 	 */

 	if (class->padding != 0 && type->alignment == 0 && cconf.has_alignment_info &&

-	    !cconf.suppress_force_paddings) {

+	    !cconf.suppress_force_paddings && last != NULL) {

 		tag_pos = cu__type(cu, last->tag.type);

 		size = tag__size(tag_pos, cu);

-- 

2.20.1