bpf: Check validity of link->type in bpf_link_show_fdinfo()
commit 8421d4c8762bd022cb491f2f0f7019ef51b4f0a7 upstream.
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.
BUG=b/386034501
TEST=None
RELEASE_NOTE=Fixed CVE-2024-53099 in the linux kernel.
cos-patch: security-high
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241024013558.1135167-3-houtao@huaweicloud.com
[ shung-hsi.yu: break up existing seq_printf() call since commit 68b04864ca42
("bpf: Create links for BPF struct_ops maps.") is not present ]
Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Change-Id: Ie2c53a11334d7d9db2a4351c88a4ba29a0c667a8
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/89559
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Kevin Berry <kpberry@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index d4b4a47..37aa1e3 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2522,16 +2522,21 @@ 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] = { };
+ 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);
+
bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
seq_printf(m,
- "link_type:\t%s\n"
- "link_id:\t%u\n"
"prog_tag:\t%s\n"
"prog_id:\t%u\n",
- bpf_link_type_strs[link->type],
- link->id,
prog_tag,
prog->aux->id);
if (link->ops->show_fdinfo)
