[PATCH 5.15 386/913] bpftool: Only set obj->skeleton on complete success

From: Greg Kroah-Hartman
Date: Tue Apr 05 2022 - 17:15:04 EST

From: Wei Fu <fuweid89@xxxxxxxxx>

[ Upstream commit 0991f6a38f576aa9a5e34713e23c998a3310d4d0 ]

After `bpftool gen skeleton`, the ${bpf_app}.skel.h will provide that
${bpf_app_name}__open helper to load bpf. If there is some error
like ENOMEM, the ${bpf_app_name}__open will rollback(free) the allocated
object, including `bpf_object_skeleton`.

Since the ${bpf_app_name}__create_skeleton set the obj->skeleton first
and not rollback it when error, it will cause double-free in
${bpf_app_name}__destory at ${bpf_app_name}__open. Therefore, we should
set the obj->skeleton before return 0;

Fixes: 5dc7a8b21144 ("bpftool, selftests/bpf: Embed object file inside skeleton")
Signed-off-by: Wei Fu <fuweid89@xxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20220108084008.1053111-1-fuweid89@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
tools/bpf/bpftool/gen.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index d40d92bbf0e4..07fa502a4ac1 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -870,7 +870,6 @@ static int do_skeleton(int argc, char **argv)
s = (struct bpf_object_skeleton *)calloc(1, sizeof(*s));\n\
if (!s) \n\
goto err; \n\
- obj->skeleton = s; \n\
s->sz = sizeof(*s); \n\
s->name = \"%1$s\"; \n\
@@ -955,6 +954,7 @@ static int do_skeleton(int argc, char **argv)
\"; \n\
+ obj->skeleton = s; \n\
return 0; \n\
err: \n\
bpf_object__destroy_skeleton(s); \n\