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bpf: Check validity of link->type in bpf_link_show_fdinfo()

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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@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241024013558.1135167-3-houtao@huaweicloud.com
This commit is contained in:
Hou Tao 2024-10-24 09:35:58 +08:00 committed by Andrii Nakryiko
parent c2f803052b
commit 8421d4c876
1 changed files with 9 additions and 5 deletions
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14
kernel/bpf/syscall.c
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@ -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,