[PATCH 6.1 0213/1146] libbpf: Fix null-pointer dereference in find_prog_by_sec_insn()

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From: Shung-Hsi Yu <shung-hsi.yu@xxxxxxxx>

[ Upstream commit d0d382f95a9270dcf803539d6781d6bd67e3f5b2 ]

When there are no program sections, obj->programs is left unallocated,
and find_prog_by_sec_insn()'s search lands on &obj->programs[0] == NULL,
and will cause null-pointer dereference in the following access to
prog->sec_idx.

Guard the search with obj->nr_programs similar to what's being done in
__bpf_program__iter() to prevent null-pointer access from happening.

Fixes: db2b8b06423c ("libbpf: Support CO-RE relocations for multi-prog sections")
Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@xxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20221012022353.7350-4-shung-hsi.yu@xxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 tools/lib/bpf/libbpf.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a0d3cc39ea73..b9a29d105376 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4115,6 +4115,9 @@ static struct bpf_program *find_prog_by_sec_insn(const struct bpf_object *obj,
 	int l = 0, r = obj->nr_programs - 1, m;
 	struct bpf_program *prog;
 
+	if (!obj->nr_programs)
+		return NULL;
+
 	while (l < r) {
 		m = l + (r - l + 1) / 2;
 		prog = &obj->programs[m];
-- 
2.35.1






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