On 12/20/23 2:41 PM, Xin Liu wrote:
> From: zhangmingyi <[email protected]>
Small nits only, otherwise lgtm.
Please prefix subject with libbpf e.g. the full one should look like
"libbpf: Fix NULL pointer dereference in bpf_object__collect_prog_relos"
> a issue occurred while reading an ELF file in libbpf.c during fuzzing:
"An issue [...]"
> Program received signal SIGSEGV, Segmentation fault.
> 0x0000000000958e97 in bpf_object.collect_prog_relos () at libbpf.c:4206
> 4206 in libbpf.c
> (gdb) bt
> #0 0x0000000000958e97 in bpf_object.collect_prog_relos () at libbpf.c:4206
> #1 0x000000000094f9d6 in bpf_object.collect_relos () at libbpf.c:6706
> #2 0x000000000092bef3 in bpf_object_open () at libbpf.c:7437
> #3 0x000000000092c046 in bpf_object.open_mem () at libbpf.c:7497
> #4 0x0000000000924afa in LLVMFuzzerTestOneInput () at fuzz/bpf-object-fuzzer.c:16
> #5 0x000000000060be11 in testblitz_engine::fuzzer::Fuzzer::run_one ()
> #6 0x000000000087ad92 in tracing::span::Span::in_scope ()
> #7 0x00000000006078aa in testblitz_engine::fuzzer::util::walkdir ()
> #8 0x00000000005f3217 in testblitz_engine::entrypoint::main::{{closure}} ()
> #9 0x00000000005f2601 in main ()
> (gdb)
>
> scn_data was null at this code(tools/lib/bpf/src/libbpf.c):
>
> if (rel->r_offset % BPF_INSN_SZ || rel->r_offset >= scn_data->d_size) {
>
> The scn_data is derived from the code above:
>
> scn = elf_sec_by_idx(obj, sec_idx);
> scn_data = elf_sec_data(obj, scn);
>
> relo_sec_name = elf_sec_str(obj, shdr->sh_name);
> sec_name = elf_sec_name(obj, scn);
> if (!relo_sec_name || !sec_name)// don't check whether scn_data is NULL
> return -EINVAL;
>
> In certain special scenarios, such as reading a malformed ELF file,
> it is possible that scn_data may be a null pointer
>
> Signed-off-by: zhangmingyi <[email protected]>
Zhang Mingyi <[email protected]> ?
If that is correct, please also make sure that this is the same in From: line.
> Signed-off-by: Xin Liu <[email protected]>
> Signed-off-by: Changye Wu <[email protected]>
> ---
> tools/lib/bpf/libbpf.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index e067be95da3c..df1b550f7460 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -4344,6 +4344,8 @@ bpf_object__collect_prog_relos(struct bpf_object *obj, Elf64_Shdr *shdr, Elf_Dat
>
> scn = elf_sec_by_idx(obj, sec_idx);
> scn_data = elf_sec_data(obj, scn);
> + if (!scn_data)
> + return -LIBBPF_ERRNO__FORMAT;
>
> relo_sec_name = elf_sec_str(obj, shdr->sh_name);
> sec_name = elf_sec_name(obj, scn);
>