[PATCH bpf-next] libbpf: fix potential uninit memory read

[PATCH bpf-next] libbpf: fix potential uninit memory read

[Andrii Nakryiko]

In case of BPF_CORE_TYPE_ID_LOCAL we fill out target result explicitly.
But targ_res itself isn't initialized in such a case, and subsequent
call to bpf_core_patch_insn() might read uninitialized field (like
fail_memsz_adjust in this case). So ensure that targ_res is
zero-initialized for BPF_CORE_TYPE_ID_LOCAL case.

This was reported by Coverity static analyzer.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/relo_core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c
index c770483b4c36..910865e29edc 100644
--- a/tools/lib/bpf/relo_core.c
+++ b/tools/lib/bpf/relo_core.c
@@ -1223,6 +1223,7 @@ int bpf_core_apply_relo_insn(const char *prog_name, struct bpf_insn *insn,
 	/* TYPE_ID_LOCAL relo is special and doesn't need candidate search */
 	if (relo->kind == BPF_CORE_TYPE_ID_LOCAL) {
 		/* bpf_insn's imm value could get out of sync during linking */
+		memset(&targ_res, 0, sizeof(targ_res));
 		targ_res.validate = false;
 		targ_res.poison = false;
 		targ_res.orig_val = local_spec->root_type_id;
-- 
2.30.2

Re: [PATCH bpf-next] libbpf: fix potential uninit memory read

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <daniel@iogearbox.net>:

On Mon, 13 Dec 2021 17:00:32 -0800 you wrote:
> In case of BPF_CORE_TYPE_ID_LOCAL we fill out target result explicitly.
> But targ_res itself isn't initialized in such a case, and subsequent
> call to bpf_core_patch_insn() might read uninitialized field (like
> fail_memsz_adjust in this case). So ensure that targ_res is
> zero-initialized for BPF_CORE_TYPE_ID_LOCAL case.
> 
> This was reported by Coverity static analyzer.
> 
> [...]

Here is the summary with links:
  - [bpf-next] libbpf: fix potential uninit memory read
    https://git.kernel.org/bpf/bpf-next/c/4581e676d3be

You are awesome, thank you!
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