On Thu, Oct 03, 2024 at 08:23:00PM +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-yb0snzt...@mail.gmail.com/ > Fixes: 1b715e1b0ec5 ("bpf: Support ->fill_link_info for perf_event") > Signed-off-by: tyrone-wu <wudevel...@gmail.com> > --- > 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
looks good, I checked with Daniel and it's better to separate kernel and selftest changes, so it's easier to get this applied in stable branches could you split the change in 2 changes and repost? please keep my ack thanks, jirka > > 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..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); > + *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, > diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c > b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c > index f3932941bbaa..59077f260404 100644 > --- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c > +++ b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c > @@ -67,8 +67,8 @@ static int verify_perf_link_info(int fd, enum > bpf_perf_event_type type, long add > > ASSERT_EQ(info.perf_event.kprobe.cookie, PERF_EVENT_COOKIE, > "kprobe_cookie"); > > + ASSERT_EQ(info.perf_event.kprobe.name_len, strlen(KPROBE_FUNC) > + 1, "name_len"); > if (!info.perf_event.kprobe.func_name) { > - ASSERT_EQ(info.perf_event.kprobe.name_len, 0, > "name_len"); > info.perf_event.kprobe.func_name = ptr_to_u64(&buf); > info.perf_event.kprobe.name_len = sizeof(buf); > goto again; > @@ -79,8 +79,8 @@ static int verify_perf_link_info(int fd, enum > bpf_perf_event_type type, long add > ASSERT_EQ(err, 0, "cmp_kprobe_func_name"); > break; > case BPF_PERF_EVENT_TRACEPOINT: > + ASSERT_EQ(info.perf_event.tracepoint.name_len, strlen(TP_NAME) > + 1, "name_len"); > if (!info.perf_event.tracepoint.tp_name) { > - ASSERT_EQ(info.perf_event.tracepoint.name_len, 0, > "name_len"); > info.perf_event.tracepoint.tp_name = ptr_to_u64(&buf); > info.perf_event.tracepoint.name_len = sizeof(buf); > goto again; > @@ -96,8 +96,8 @@ static int verify_perf_link_info(int fd, enum > bpf_perf_event_type type, long add > case BPF_PERF_EVENT_URETPROBE: > ASSERT_EQ(info.perf_event.uprobe.offset, offset, > "uprobe_offset"); > > + ASSERT_EQ(info.perf_event.uprobe.name_len, strlen(UPROBE_FILE) > + 1, "name_len"); > if (!info.perf_event.uprobe.file_name) { > - ASSERT_EQ(info.perf_event.uprobe.name_len, 0, > "name_len"); > info.perf_event.uprobe.file_name = ptr_to_u64(&buf); > info.perf_event.uprobe.name_len = sizeof(buf); > goto again; > -- > 2.43.0 >
