[PATCH bpf-next v1 1/2] bpf: Fix bounds for bpf_prog_get_file_line linfo loop

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

We may overrun the bounds because linfo and jited_linfo are already
advanced to prog->aux->linfo_idx, hence we must only iterate the
remaining elements until we reach prog->aux->nr_linfo. Adjust the
nr_linfo calculation to fix this. Reported in [0].

  [0]: https://lore.kernel.org/bpf/f3527af3b0620ce36e299e97e7532d2555018de2.camel@gmail.com

Reported-by: Eduard Zingerman <eddyz87@gmail.com>
Fixes: 0e521efaf363 ("bpf: Add function to extract program source info")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index fe8a53f3c5bc..61613785bdd0 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -3244,6 +3244,7 @@ int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char *
 	struct bpf_line_info *linfo;
 	void **jited_linfo;
 	struct btf *btf;
+	int nr_linfo;
 
 	btf = prog->aux->btf;
 	linfo = prog->aux->linfo;
@@ -3258,8 +3259,9 @@ int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char *
 
 	insn_start = linfo[0].insn_off;
 	insn_end = insn_start + len;
+	nr_linfo = prog->aux->nr_linfo - prog->aux->linfo_idx;
 
-	for (int i = 0; i < prog->aux->nr_linfo &&
+	for (int i = 0; i < nr_linfo &&
 	     linfo[i].insn_off >= insn_start && linfo[i].insn_off < insn_end; i++) {
 		if (jited_linfo[i] >= (void *)ip)
 			break;
-- 
2.47.1