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: 1b715e1b0ec5 ("bpf: Support ->fill_link_info for perf_event")
Signed-off-by: Tyrone Wu <wudevelops@xxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Acked-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
V6 -> V7:
- Use *ulenp suggestion from Jiri for user name_len
- Set user name_len to 1 when buf returned from bpf_get_perf_event_info() is NULL
V5 -> V6:
- Use simpler buf check while keeping V4
- Fix netdev/checkpatch warning for 80 cols exceeded
- Fix Signed-off-by to use real name instead of git username
V4 -> V5:
- Check that buf is not NULL before retrieving/using its length
V3 -> V4:
- Split patch into separate kernel and selftest change
V2 -> V3:
- Use clearer variable name for user set/inputted name len (name_len -> input_len)
- Change (name_len -> input_len) type from size_t to u32 since it's only received and used as u32
V1 -> V2:
- Use user set *ulen in bpf_copy_to_user before overwriting *ulen
kernel/bpf/syscall.c | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a8f1808a1ca5..8cfa7183d2ef 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -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,
--
2.43.0
