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bpf: fix unpopulated name_len field in perf_event link info

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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.

Fixes: 1b715e1b0e ("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>
Link: https://lore.kernel.org/r/20241008164312.46269-1-wudevelops@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Tyrone Wu 2024-10-08 16:43:11 +00:00 committed by Alexei Starovoitov
parent 434247637c
commit 4deecdd29c
1 changed files with 23 additions and 8 deletions
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31
kernel/bpf/syscall.c
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@ -3565,15 +3565,16 @@ 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;
ulen = *ulenp;
if (!ulen ^ !uname)
return -EINVAL;
@ -3581,10 +3582,17 @@ static int bpf_perf_link_fill_common(const struct perf_event *event,
probe_offset, probe_addr, missed);
if (err)
return err;
if (!uname)
return 0;
if (buf) {
len = strlen(buf);
*ulenp = len + 1;
} else {
*ulenp = 1;
}
if (!uname)
return 0;
if (buf) {
err = bpf_copy_to_user(uname, buf, ulen, len);
if (err)
return err;
@ -3609,7 +3617,7 @@ 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 +3625,7 @@ 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 +3647,7 @@ 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 +3656,7 @@ 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 +3682,18 @@ 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,