Commit c34c338a authored by Daniel Xu's avatar Daniel Xu Committed by Daniel Borkmann
Browse files

libbpf: Do not close un-owned FD 0 on errors 



Before this patch, btf_new() was liable to close an arbitrary FD 0 if
BTF parsing failed. This was because:

* btf->fd was initialized to 0 through the calloc()
* btf__free() (in the `done` label) closed any FDs >= 0
* btf->fd is left at 0 if parsing fails

This issue was discovered on a system using libbpf v0.3 (without
BTF_KIND_FLOAT support) but with a kernel that had BTF_KIND_FLOAT types
in BTF. Thus, parsing fails.

While this patch technically doesn't fix any issues b/c upstream libbpf
has BTF_KIND_FLOAT support, it'll help prevent issues in the future if
more BTF types are added. It also allow the fix to be backported to
older libbpf's.

Fixes: 3289959b ("libbpf: Support BTF loading and raw data output in both endianness")
Signed-off-by: default avatarDaniel Xu <dxu@dxuuu.xyz>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/5969bb991adedb03c6ae93e051fd2a00d293cf25.1627513670.git.dxu@dxuuu.xyz
parent 78d14bda

tools/lib/bpf/btf.c

+1 −2
Original line number Diff line number Diff line
@@ -804,6 +804,7 @@ static struct btf *btf_new(const void *data, __u32 size, struct btf *base_btf) 
	btf->nr_types = 0;

	btf->start_id = 1;

	btf->start_str_off = 0;

	btf->fd = -1;



	if (base_btf) {

		btf->base_btf = base_btf;
@@ -832,8 +833,6 @@ static struct btf *btf_new(const void *data, __u32 size, struct btf *base_btf) 
	if (err)

		goto done;



	btf->fd = -1;



done:

	if (err) {

		btf__free(btf);