On Fri, Oct 4, 2024 at 11:40 PM tyrone-wu <wudevelops@xxxxxxxxx> wrote: > > 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. > > Link: https://lore.kernel.org/bpf/CABVU1kXwQXhqQGe0RTrr7eegtM6SVW_KayZBy16-yb0Snztmtg@xxxxxxxxxxxxxx/ > Fixes: 1b715e1b0ec5 ("bpf: Support ->fill_link_info for perf_event") > Signed-off-by: tyrone-wu <wudevelops@xxxxxxxxx> > Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx> > --- > V3 -> V4: > Link: https://lore.kernel.org/bpf/Zv_PP6Gs5cq3W2Ey@krava/ > - Split patch into separate kernel and selftest change > > V2 -> V3: > Link: https://lore.kernel.org/bpf/Zv7sISV0yEyGlEM3@krava/ > - 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: > Link: https://lore.kernel.org/bpf/Zv0wl-S13WJnIkb_@krava/ > - Use user set *ulen in bpf_copy_to_user before overwriting *ulen > > kernel/bpf/syscall.c | 29 ++++++++++++++++++++--------- > 1 file changed, 20 insertions(+), 9 deletions(-) > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index a8f1808a1ca5..56c556fcf325 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -3565,27 +3565,31 @@ 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 *ulen, > u64 *probe_offset, u64 *probe_addr, > u32 *fd_type, unsigned long *missed) > { > const char *buf; > - u32 prog_id; > + u32 prog_id, input_len; > size_t len; > int err; > > - if (!ulen ^ !uname) > + if (!(*ulen) ^ !uname) > return -EINVAL; > > err = bpf_get_perf_event_info(event, &prog_id, fd_type, &buf, > probe_offset, probe_addr, missed); > if (err) > return err; > + > + input_len = *ulen; > + len = strlen(buf); The buf might be NULL, so we should check it. > + *ulen = len + 1; > if (!uname) > return 0; > + > if (buf) { > - len = strlen(buf); > - err = bpf_copy_to_user(uname, buf, ulen, len); > + err = bpf_copy_to_user(uname, buf, input_len, len); > if (err) > return err; > } else { > @@ -3609,7 +3613,7 @@ 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 +3621,7 @@ 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 +3643,7 @@ 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 +3652,7 @@ 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 +3678,18 @@ 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 > -- Regards Yafang
