On 12/20/23 2:41 PM, Xin Liu wrote:
From: zhangmingyi <zhangmingyi5@xxxxxxxxxx>
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 <zhangmingyi5@xxxxxxxxxx>
Zhang Mingyi <zhangmingyi5@xxxxxxxxxx> ?
If that is correct, please also make sure that this is the same in From: line.
Signed-off-by: Xin Liu <liuxin350@xxxxxxxxxx>
Signed-off-by: Changye Wu <wuchangye@xxxxxxxxxx>
---
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);
