On Wed, Oct 02, 2024 at 09:38:39PM +0000, tyrone-wu 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. The > relevant selftests have also been updated to assert that `name_len` > contains the correct size rather than 0. > > 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> > --- > 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 +++++++++++++------ > .../selftests/bpf/prog_tests/fill_link_info.c | 6 ++-- > 2 files changed, 23 insertions(+), 12 deletions(-) > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index a8f1808a1ca5..26cc18693924 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; > - size_t len; > + size_t len, name_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; > + > + name_len = *ulen; > + len = strlen(buf); > + *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, name_len, len); > if (err) > return err; > } else { small nit.. up to you but I'd suggest bit different naming like below, otherwise looks good Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx> thanks, jirka --- diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index a8f1808a1ca5..b637e9dced5a 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3565,26 +3565,28 @@ 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; - if (!ulen ^ !uname) + if (!(*ulenp) ^ !uname) return -EINVAL; err = bpf_get_perf_event_info(event, &prog_id, fd_type, &buf, probe_offset, probe_addr, missed); if (err) return err; + ulen = *ulenp; + len = strlen(buf); + *ulenp = len + 1; if (!uname) return 0; if (buf) { - len = strlen(buf); err = bpf_copy_to_user(uname, buf, ulen, len); if (err) return err;
