On Thu, Apr 21, 2022 at 9:53 AM Daniel Borkmann <[email protected]> wrote:
>
> On 4/21/22 3:23 PM, Artem Savkov wrote:
> > I am getting the following compilation error for prog_tests/uprobe_autoattach.c
> >
> > tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c: In function ‘test_uprobe_autoattach’:
> > ./test_progs.h:209:26: error: pointer ‘mem’ may be used after ‘free’ [-Werror=use-after-free]
> >
> > mem variable is now used in one of the asserts so it shouldn't be freed right
> > away. Move free(mem) after the assert block.
>
> Looks good, but I rephrased this a bit to avoid confusion. It's false positive given we
> only compare the addresses but don't deref mem, which the compiler might not be able to
> follow in this case.
>
Great, thanks Daniel!
> https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=6a12b8e20d7e72386594a9dbe7bf2d7fae3b3aa6
>
> Thanks,
> Daniel
>
> > Fixes: 1717e248014c ("selftests/bpf: Uprobe tests should verify param/return values")
> > Signed-off-by: Artem Savkov <[email protected]>
> > ---
> > tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c b/tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c
> > index d6003dc8cc99..35b87c7ba5be 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_autoattach.c
> > @@ -34,7 +34,6 @@ void test_uprobe_autoattach(void)
> >
> > /* trigger & validate shared library u[ret]probes attached by name */
> > mem = malloc(malloc_sz);
> > - free(mem);
> >
> > ASSERT_EQ(skel->bss->uprobe_byname_parm1, trigger_val, "check_uprobe_byname_parm1");
> > ASSERT_EQ(skel->bss->uprobe_byname_ran, 1, "check_uprobe_byname_ran");
> > @@ -44,6 +43,8 @@ void test_uprobe_autoattach(void)
> > ASSERT_EQ(skel->bss->uprobe_byname2_ran, 3, "check_uprobe_byname2_ran");
> > ASSERT_EQ(skel->bss->uretprobe_byname2_rc, mem, "check_uretprobe_byname2_rc");
> > ASSERT_EQ(skel->bss->uretprobe_byname2_ran, 4, "check_uretprobe_byname2_ran");
> > +
> > + free(mem);
> > cleanup:
> > test_uprobe_autoattach__destroy(skel);
> > }
> >
>