From: Mingyi Zhang <zhangmingyi5@xxxxxxxxxx>
During our fuzz testing, we encountered the following error:
Program received signal SIGSEGV, Segmentation fault.
0x00000000005915bb in __interceptor_strcmp.part.0 ()
(gdb) bt
#0 0x00000000005915bb in __interceptor_strcmp.part.0 ()
#1 0x000000000087dc65 in __wrap_strcmp ()
#2 0x0000000000951ded in find_extern_btf_id () at libbpf.c:3508
#3 0x000000000094d7a1 in bpf_object.collect_externs () at libbpf.c:3712
#4 0x000000000092be3b in bpf_object_open () at libbpf.c:7433
#5 0x000000000092c046 in bpf_object.open_mem () at libbpf.c:7497
#6 0x0000000000924afa in LLVMFuzzerTestOneInput () at fuzz/bpf-object-fuzzer.c:16
#7 0x000000000060be11 in testblitz_engine::fuzzer::Fuzzer::run_one ()
#8 0x000000000087ad92 in tracing::span::Span::in_scope ()
#9 0x00000000006078aa in testblitz_engine::fuzzer::util::walkdir ()
#10 0x00000000005f3217 in testblitz_engine::entrypoint::main::{{closure}} ()
#11 0x00000000005f2601 in main ()
(gdb)
tname = btf__name_by_offset(btf, t->name_off);
if (strcmp(tname, ext_name))
continue;
tname is passed directly into strcmp without a null pointer check.
When t(btf_type)->name_off >= btf->hdr->str_len, tname is NULL. normally,
that's not likely to happen.
Considering that the bpf_object__open_mem interface is a direct API
provided to users, which reads directly from memory. There may be an
input similar to this fuzzing, leading to a Segmentation fault.
Signed-off-by: Mingyi Zhang <zhangmingyi5@xxxxxxxxxx>
Signed-off-by: Xin Liu <liuxin350@xxxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 604368cfbf02..c65d2f2abea4 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3944,7 +3944,7 @@ static int find_extern_btf_id(const struct btf *btf, const char *ext_name)
continue;
tname = btf__name_by_offset(btf, t->name_off);
- if (strcmp(tname, ext_name))
+ if (tname && strcmp(tname, ext_name))
continue;
if (btf_is_var(t) &&
--
2.33.0
