On Mon, Oct 7, 2024 at 11:29 AM Tyrone Wu wudevelops@gmail.com wrote:
From: tyrone-wu wudevelops@gmail.com
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-yb0Snzt... Fixes: 1b715e1b0ec5 ("bpf: Support ->fill_link_info for perf_event") Signed-off-by: Tyrone Wu wudevelops@gmail.com Acked-by: Jiri Olsa jolsa@kernel.org Acked-by: Yafang Shao laoar.shao@gmail.com
V5 -> V6: Link: https://lore.kernel.org/bpf/ZwOWs_XrBtlTGE24@krava/
- 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: Link: https://lore.kernel.org/bpf/CALOAHbC5xm7Cbfhau3z5X2PqUhiHECNWAPtJCWiOVqTKmdZ...
- 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/
Please drop all the Link: tags, our scripts will accumulate all of them in the final commit and it becomes very confusing. Our script will add the final Link: for your latest applied version anyways.
Also, git still shows:
Author: tyrone-wu wudevelops@gmail.com
So please try to fix that.
But generally, looks good and I almost applied, but see one small issue below, which I think needs fixing.
pw-bot: cr
- Use user set *ulen in bpf_copy_to_user before overwriting *ulen
kernel/bpf/syscall.c | 32 +++++++++++++++++++++++--------- 1 file changed, 23 insertions(+), 9 deletions(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index a8f1808a1ca5..b5a7e428ac16 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3565,27 +3565,33 @@ 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,
nit: I'd do what Jiri suggested, use `u32 *ulenp` here
u64 *probe_offset, u64 *probe_addr, u32 *fd_type, unsigned long *missed){ const char *buf;
u32 prog_id;
u32 prog_id, input_len;
and then just `u32 ulen;` here.
size_t len; int err;
start with just
ulen = *ulenp;
if (!ulen ^ !uname)
if (!(*ulen) ^ !uname)
and remove all the `*ulen` uses except the final assignment
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;}
don't we need
} else { *ulen = 1; }
for cases when we don't have buf returned from bpf_get_perf_event_info()? Though I don't think it can happen currently, existing code is clearly ready to handle that case, so let's keep it consistent.
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 +3615,7 @@ 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 +3623,7 @@ 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 +3645,7 @@ 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 +3654,7 @@ 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 +3680,19 @@ 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);
nit: keep it on a single line
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