diff mbox series

[v2,bpf-next,2/5] libbpf: improve sanity checking during BTF fix up

Message ID 20211103173213.1376990-3-andrii@kernel.org (mailing list archive)
State Accepted
Delegated to: BPF
Headers show
Series libbpf ELF sanity checking improvements | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR success PR summary
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers warning 5 maintainers not CCed: songliubraving@fb.com john.fastabend@gmail.com kafai@fb.com kpsingh@kernel.org netdev@vger.kernel.org
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 15 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next success VM_Test

Commit Message

Andrii Nakryiko Nov. 3, 2021, 5:32 p.m. UTC 
If BTF is corrupted DATASEC's variable type ID might be incorrect.
Prevent this easy to detect situation with extra NULL check.
Reported by oss-fuzz project.

Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/libbpf.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 71f5a009010a..f836a1936597 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2752,13 +2752,12 @@  static int btf_fixup_datasec(struct bpf_object *obj, struct btf *btf,
 
 	for (i = 0, vsi = btf_var_secinfos(t); i < vars; i++, vsi++) {
 		t_var = btf__type_by_id(btf, vsi->type);
-		var = btf_var(t_var);
-
-		if (!btf_is_var(t_var)) {
+		if (!t_var || !btf_is_var(t_var)) {
 			pr_debug("Non-VAR type seen in section %s\n", name);
 			return -EINVAL;
 		}
 
+		var = btf_var(t_var);
 		if (var->linkage == BTF_VAR_STATIC)
 			continue;