On 8/20/20 11:31 PM, Andrii Nakryiko wrote:
On Thu, Aug 20, 2020 at 3:50 PM Yonghong Song <yhs@xxxxxx> wrote:
This patch implemented bpf_link callback functions
show_fdinfo and fill_link_info to support link_query
interface.
The general interface for show_fdinfo and fill_link_info
will print/fill the target_name. Each targets can
register show_fdinfo and fill_link_info callbacks
to print/fill more target specific information.
For example, the below is a fdinfo result for a bpf
task iterator.
$ cat /proc/1749/fdinfo/7
pos: 0
flags: 02000000
mnt_id: 14
link_type: iter
link_id: 11
prog_tag: 990e1f8152f7e54f
prog_id: 59
target_name: task
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
include/linux/bpf.h | 6 ++++
include/uapi/linux/bpf.h | 7 ++++
kernel/bpf/bpf_iter.c | 58 ++++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 7 ++++
4 files changed, 78 insertions(+)
[...]
+
+static int bpf_iter_link_fill_link_info(const struct bpf_link *link,
+ struct bpf_link_info *info)
+{
+ struct bpf_iter_link *iter_link =
+ container_of(link, struct bpf_iter_link, link);
+ char __user *ubuf = u64_to_user_ptr(info->iter.target_name);
+ bpf_iter_fill_link_info_t fill_link_info;
+ u32 ulen = info->iter.target_name_len;
+ const char *target_name;
+ u32 target_len;
+
+ if (ulen && !ubuf)
+ return -EINVAL;
+
+ target_name = iter_link->tinfo->reg_info->target;
+ target_len = strlen(target_name);
+ info->iter.target_name_len = target_len + 1;
+ if (!ubuf)
+ return 0;
this might return prematurely before fill_link_info() below gets a
chance to fill in some extra info?
The extra info filled by below fill_link_info is target specific
and we need a target name to ensure picking right union members.
So it is best to enforce a valid target name before filling
target dependent fields. See below, if there are any errors
for copy_to_user or enospc, we won't copy addition link info
either.
+
+ if (ulen >= target_len + 1) {
+ if (copy_to_user(ubuf, target_name, target_len + 1))
+ return -EFAULT;
+ } else {
+ char zero = '\0';
+
+ if (copy_to_user(ubuf, target_name, ulen - 1))
+ return -EFAULT;
+ if (put_user(zero, ubuf + ulen - 1))
+ return -EFAULT;
+ return -ENOSPC;
+ }
+
+ fill_link_info = iter_link->tinfo->reg_info->fill_link_info;
+ if (fill_link_info)
+ return fill_link_info(&iter_link->aux, info);
+
+ return 0;
+}
+
[...]
