Commit 4deecdd2 authored by Tyrone Wu's avatar Tyrone Wu Committed by Alexei Starovoitov
Browse files

bpf: fix unpopulated name_len field in perf_event link info 



Previously when retrieving `bpf_link_info.perf_event` for
kprobe/uprobe/tracepoint, the `name_len` field was not populated by the
kernel, leaving it to reflect the value initially set by the user. This
behavior was inconsistent with how other input/output string buffer
fields function (e.g. `raw_tracepoint.tp_name_len`).

This patch fills `name_len` with the actual size of the string name.

Fixes: 1b715e1b ("bpf: Support ->fill_link_info for perf_event")
Signed-off-by: default avatarTyrone Wu <wudevelops@gmail.com>
Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
Acked-by: default avatarYafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20241008164312.46269-1-wudevelops@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 43424763

kernel/bpf/syscall.c

+22 −7
Original line number Diff line number Diff line
@@ -3565,15 +3565,16 @@ static void bpf_perf_link_dealloc(struct bpf_link *link) 
}



static int bpf_perf_link_fill_common(const struct perf_event *event,

				     char __user *uname, u32 ulen,

				     char __user *uname, u32 *ulenp,

				     u64 *probe_offset, u64 *probe_addr,

				     u32 *fd_type, unsigned long *missed)

{

	const char *buf;

	u32 prog_id;

	u32 prog_id, ulen;

	size_t len;

	int err;



	ulen = *ulenp;

	if (!ulen ^ !uname)

		return -EINVAL;
@@ -3581,10 +3582,17 @@ static int bpf_perf_link_fill_common(const struct perf_event *event, 
				      probe_offset, probe_addr, missed);

	if (err)

		return err;



	if (buf) {

		len = strlen(buf);

		*ulenp = len + 1;

	} else {

		*ulenp = 1;

	}

	if (!uname)

		return 0;



	if (buf) {

		len = strlen(buf);

		err = bpf_copy_to_user(uname, buf, ulen, len);

		if (err)

			return err;
@@ -3609,7 +3617,7 @@ static int bpf_perf_link_fill_kprobe(const struct perf_event *event, 


	uname = u64_to_user_ptr(info->perf_event.kprobe.func_name);

	ulen = info->perf_event.kprobe.name_len;

	err = bpf_perf_link_fill_common(event, uname, ulen, &offset, &addr,

	err = bpf_perf_link_fill_common(event, uname, &ulen, &offset, &addr,

					&type, &missed);

	if (err)

		return err;
@@ -3617,7 +3625,7 @@ static int bpf_perf_link_fill_kprobe(const struct perf_event *event, 
		info->perf_event.type = BPF_PERF_EVENT_KRETPROBE;

	else

		info->perf_event.type = BPF_PERF_EVENT_KPROBE;



	info->perf_event.kprobe.name_len = ulen;

	info->perf_event.kprobe.offset = offset;

	info->perf_event.kprobe.missed = missed;

	if (!kallsyms_show_value(current_cred()))
@@ -3639,7 +3647,7 @@ static int bpf_perf_link_fill_uprobe(const struct perf_event *event, 


	uname = u64_to_user_ptr(info->perf_event.uprobe.file_name);

	ulen = info->perf_event.uprobe.name_len;

	err = bpf_perf_link_fill_common(event, uname, ulen, &offset, &addr,

	err = bpf_perf_link_fill_common(event, uname, &ulen, &offset, &addr,

					&type, NULL);

	if (err)

		return err;
@@ -3648,6 +3656,7 @@ static int bpf_perf_link_fill_uprobe(const struct perf_event *event, 
		info->perf_event.type = BPF_PERF_EVENT_URETPROBE;

	else

		info->perf_event.type = BPF_PERF_EVENT_UPROBE;

	info->perf_event.uprobe.name_len = ulen;

	info->perf_event.uprobe.offset = offset;

	info->perf_event.uprobe.cookie = event->bpf_cookie;

	return 0;
@@ -3673,12 +3682,18 @@ static int bpf_perf_link_fill_tracepoint(const struct perf_event *event, 
{

	char __user *uname;

	u32 ulen;

	int err;



	uname = u64_to_user_ptr(info->perf_event.tracepoint.tp_name);

	ulen = info->perf_event.tracepoint.name_len;

	err = bpf_perf_link_fill_common(event, uname, &ulen, NULL, NULL, NULL, NULL);

	if (err)

		return err;



	info->perf_event.type = BPF_PERF_EVENT_TRACEPOINT;

	info->perf_event.tracepoint.name_len = ulen;

	info->perf_event.tracepoint.cookie = event->bpf_cookie;

	return bpf_perf_link_fill_common(event, uname, ulen, NULL, NULL, NULL, NULL);

	return 0;

}



static int bpf_perf_link_fill_perf_event(const struct perf_event *event,