From: Hou Tao <houtao1@xxxxxxxxxx>
If a newly-added link type doesn't invoke BPF_LINK_TYPE(), accessing
bpf_link_type_strs[link->type] may result in an out-of-bounds access.
To spot such missed invocations early in the future, checking the
validity of link->type in bpf_link_show_fdinfo() and emitting a warning
when such invocations are missed.
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
kernel/bpf/syscall.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 8cfa7183d2ef..9b6592c7e562 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3069,13 +3069,17 @@ static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp)
{
const struct bpf_link *link = filp->private_data;
const struct bpf_prog *prog = link->prog;
+ enum bpf_link_type type = link->type;
char prog_tag[sizeof(prog->tag) * 2 + 1] = { };
- seq_printf(m,
- "link_type:\t%s\n"
- "link_id:\t%u\n",
- bpf_link_type_strs[link->type],
- link->id);
+ if (type < ARRAY_SIZE(bpf_link_type_strs) && bpf_link_type_strs[type]) {
+ seq_printf(m, "link_type:\t%s\n", bpf_link_type_strs[type]);
+ } else {
+ WARN_ONCE(1, "missing BPF_LINK_TYPE(...) for link type %u\n", type);
+ seq_printf(m, "link_type:\t<%u>\n", type);
+ }
+ seq_printf(m, "link_id:\t%u\n", link->id);
+
if (prog) {
bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
seq_printf(m,
--
2.29.2
