linux-kernel - [PATCH 5.16 0410/1017] bpftool: Only set obj->skeleton on complete success

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Date:   Tue,  5 Apr 2022 09:22:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Wei Fu <fuweid89@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.16 0410/1017] bpftool: Only set obj->skeleton on complete success

From: Wei Fu <fuweid89@...il.com>

[ 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@...il.com>
Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
Link: https://lore.kernel.org/bpf/20220108084008.1053111-1-fuweid89@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 5c18351290f0..587027050f43 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -928,7 +928,6 @@ 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\
 									    \n\
 			s->sz = sizeof(*s);				    \n\
 			s->name = \"%1$s\";				    \n\
@@ -1001,6 +1000,7 @@ static int do_skeleton(int argc, char **argv)
 									    \n\
 			s->data = (void *)%2$s__elf_bytes(&s->data_sz);	    \n\
 									    \n\
+			obj->skeleton = s;				    \n\
 			return 0;					    \n\
 		err:							    \n\
 			bpf_object__destroy_skeleton(s);		    \n\
-- 
2.34.1