On Mon, Sep 30, 2024 at 11:59:20PM +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... Fixes: 1b715e1b0ec5 ("bpf: Support ->fill_link_info for perf_event") Signed-off-by: tyrone-wu wudevelops@gmail.com
kernel/bpf/syscall.c | 25 +++++++++++++------ .../selftests/bpf/prog_tests/fill_link_info.c | 6 ++--- 2 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index a8f1808a1ca5..90b6add4d0c9 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3565,7 +3565,7 @@ 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){ @@ -3574,18 +3574,20 @@ static int bpf_perf_link_fill_common(const struct perf_event *event, 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;
- len = strlen(buf);
- *ulen = len + 1;
I think before you overwrite *ulen with actual name lenth you should store its value and use it in bpf_copy_to_user, otherwise we could overwrite user space memory that we are not supposed to
jirka
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, *ulen, len);@@ -3609,7 +3611,7 @@ 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;
SNIP