On 3/21/22 7:31 AM, Daniel Borkmann wrote:
On 3/20/22 4:20 AM, Yonghong Song wrote:
Compiled with clang by adding LLVM=1 both kernel and selftests/bpf
build, I hit the following compilation error:
In file included from
/.../tools/testing/selftests/bpf/prog_tests/subskeleton.c:6:
./test_subskeleton_lib.subskel.h:168:6: error: variable 'err' is
used uninitialized whenever
'if' condition is true [-Werror,-Wsometimes-uninitialized]
if (!s->progs)
^~~~~~~~~
./test_subskeleton_lib.subskel.h:181:11: note: uninitialized use
occurs here
errno = -err;
^~~
./test_subskeleton_lib.subskel.h:168:2: note: remove the 'if' if
its condition is always false
if (!s->progs)
^~~~~~~~~~~~~~
The compilation error is triggered by the following code
...
int err;
obj = (struct test_subskeleton_lib *)calloc(1, sizeof(*obj));
if (!obj) {
errno = ENOMEM;
goto err;
}
...
err:
test_subskeleton_lib__destroy(obj);
errno = -err;
...
in test_subskeleton_lib__open(). The 'err' is not initialized, yet it
is used in 'errno = -err' later.
The fix is to remove 'errno = -err' since errno has been set properly
in all incoming branches.
If we remove this one here in which locations is it missing then? Do
these then
need an extra errno = -err statement before they goto err?
Everything should be covered. The following are all 'goto err' returns:
obj = (struct test_subskeleton_lib *)calloc(1, sizeof(*obj));
if (!obj) {
errno = ENOMEM;
goto err;
}
s = (struct bpf_object_subskeleton *)calloc(1, sizeof(*s));
if (!s) {
errno = ENOMEM;
goto err;
}
...
s->vars = (struct bpf_var_skeleton *)calloc(10, sizeof(*s->vars));
if (!s->vars) {
errno = ENOMEM;
goto err;
}
...
==> for all maps
/* maps */
s->map_cnt = 7;
s->map_skel_sz = sizeof(*s->maps);
s->maps = (struct bpf_map_skeleton *)calloc(s->map_cnt,
s->map_skel_sz);
if (!s->maps)
goto err;
==> calloc should set error number properly if failed.
...
==> for all progs
/* programs */
s->prog_cnt = 1;
s->prog_skel_sz = sizeof(*s->progs);
s->progs = (struct bpf_prog_skeleton *)calloc(s->prog_cnt,
s->prog_skel_sz);
if (!s->progs)
goto err;
==> calloc should set error number properly if failed.
err = bpf_object__open_subskeleton(s);
if (err)
goto err;
return obj;
==> bpf_object__open_subskeleton() in libbpf.c does set errno probably
if 'err' is not 0.
Cc: Delyan Kratunov <delyank@xxxxxx>
Fixes: 00389c58ffe9 ("00389c58ffe993782a8ba4bb5a34a102b1f6fe24")
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
tools/bpf/bpftool/gen.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 96bd2b33ccf6..7ba7ff55d2ea 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -1538,7 +1538,6 @@ static int do_subskeleton(int argc, char **argv)
return obj; \n\
err: \n\
%1$s__destroy(obj); \n\
- errno = -err; \n\
return NULL; \n\
} \n\
\n\
