On Sun, Oct 06, 2024 at 07:51:30PM +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. > > 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> > --- > V4 -> V5: > Link: https://lore.kernel.org/bpf/CALOAHbC5xm7Cbfhau3z5X2PqUhiHECNWAPtJCWiOVqTKmdZp-Q@xxxxxxxxxxxxxx/ > - Check that buf is not NULL before retrieving/using its length > > 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 | 38 ++++++++++++++++++++++++-------------- > 1 file changed, 24 insertions(+), 14 deletions(-) > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index a8f1808a1ca5..3df192a6bdcc 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -3565,32 +3565,35 @@ 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; > - if (!uname) > - return 0; > + > if (buf) { > + input_len = *ulen; > len = strlen(buf); > - err = bpf_copy_to_user(uname, buf, ulen, len); > - if (err) > - return err; > - } else { > - char zero = '\0'; > + *ulen = len + 1; > > + if (uname) { > + err = bpf_copy_to_user(uname, buf, input_len, len); > + if (err) > + return err; > + } > + } else if (uname) { > + char zero = '\0'; > if (put_user(zero, uname)) > return -EFAULT; > } hm, why not just simple check buf for and keep the rest? seems less complicated.. jirka --- diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index a8f1808a1ca5..e393b94b90ec 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; + if (buf) { + 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 {
