From: Hou Tao <houtao1@xxxxxxxxxx>
If a corresponding link type doesn't invoke BPF_LINK_TYPE(), accessing
bpf_link_type_strs[link->type] may result in out-of-bound access.
To prevent such missed invocations in the future, the following static
assertion seems feasible:
BUILD_BUG_ON(ARRAY_SIZE(bpf_link_type_strs) != __MAX_BPF_LINK_TYPE)
However, this doesn't work well. The reason is that the invocation of
BPF_LINK_TYPE() for one link type is optional due to its CONFIG_XXX
dependency and the elements in bpf_link_type_strs[] will be sparse. For
example, if CONFIG_NET is disabled, the size of bpf_link_type_strs will
be BPF_LINK_TYPE_UPROBE_MULTI + 1.
Therefore, in addition to the static assertion, remove all CONFIG_XXX
conditions for the invocation of BPF_LINK_TYPE(). If these CONFIG_XXX
conditions become necessary later, the fix may need to be revised (e.g.,
to check the validity of link_type in bpf_link_show_fdinfo()).
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
include/linux/bpf_types.h | 6 ------
kernel/bpf/syscall.c | 2 ++
2 files changed, 2 insertions(+), 6 deletions(-)
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index fa78f49d4a9a..6b7eabe9a115 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -136,21 +136,15 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_ARENA, arena_map_ops)
BPF_LINK_TYPE(BPF_LINK_TYPE_RAW_TRACEPOINT, raw_tracepoint)
BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING, tracing)
-#ifdef CONFIG_CGROUP_BPF
BPF_LINK_TYPE(BPF_LINK_TYPE_CGROUP, cgroup)
-#endif
BPF_LINK_TYPE(BPF_LINK_TYPE_ITER, iter)
-#ifdef CONFIG_NET
BPF_LINK_TYPE(BPF_LINK_TYPE_NETNS, netns)
BPF_LINK_TYPE(BPF_LINK_TYPE_XDP, xdp)
BPF_LINK_TYPE(BPF_LINK_TYPE_NETFILTER, netfilter)
BPF_LINK_TYPE(BPF_LINK_TYPE_TCX, tcx)
BPF_LINK_TYPE(BPF_LINK_TYPE_NETKIT, netkit)
BPF_LINK_TYPE(BPF_LINK_TYPE_SOCKMAP, sockmap)
-#endif
-#ifdef CONFIG_PERF_EVENTS
BPF_LINK_TYPE(BPF_LINK_TYPE_PERF_EVENT, perf)
-#endif
BPF_LINK_TYPE(BPF_LINK_TYPE_KPROBE_MULTI, kprobe_multi)
BPF_LINK_TYPE(BPF_LINK_TYPE_STRUCT_OPS, struct_ops)
BPF_LINK_TYPE(BPF_LINK_TYPE_UPROBE_MULTI, uprobe_multi)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 8cfa7183d2ef..9f335c379b05 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3071,6 +3071,8 @@ static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp)
const struct bpf_prog *prog = link->prog;
char prog_tag[sizeof(prog->tag) * 2 + 1] = { };
+ BUILD_BUG_ON(ARRAY_SIZE(bpf_link_type_strs) != __MAX_BPF_LINK_TYPE);
+
seq_printf(m,
"link_type:\t%s\n"
"link_id:\t%u\n",
--
2.29.2
