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Message-ID: <Zv7sISV0yEyGlEM3@krava>
Date: Thu, 3 Oct 2024 21:10:25 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: tyrone-wu <wudevelops@...il.com>
Cc: olsajiri@...il.com, andrii.nakryiko@...il.com, andrii@...nel.org,
ast@...nel.org, bpf@...r.kernel.org, daniel@...earbox.net,
eddyz87@...il.com, haoluo@...gle.com, john.fastabend@...il.com,
kernel-patches-bot@...com, kpsingh@...nel.org, laoar.shao@...il.com,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
martin.lau@...ux.dev, mykolal@...com, sdf@...ichev.me,
shuah@...nel.org, song@...nel.org, yonghong.song@...ux.dev
Subject: Re: [PATCH bpf v2] bpf: fix unpopulated name_len field in perf_event
link info
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@mail.gmail.com/
> Fixes: 1b715e1b0ec5 ("bpf: Support ->fill_link_info for perf_event")
> Signed-off-by: tyrone-wu <wudevelops@...il.com>
> ---
> 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@...nel.org>
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;
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