[PATCH bpf] bpf: Add missing access_ok call to copy_user_syms

[Jiri Olsa <jolsa@kernel.org>]

As reported by sashiko we use __get_user without prior access_ok call on the
user space pointer. Adding the missing call for the whole pointer array.

Plus removing the err check in the error path, because it's not needed and
also we can return -ENOMEM directly from the first kvmalloc_array fail path.

Cc: stable@vger.kernel.org
[1] https://lore.kernel.org/bpf/20260611115503.AC16D1F00893@smtp.kernel.org/
Fixes: 0236fec57a15 ("bpf: Resolve symbols with ftrace_lookup_symbols for kprobe multi link")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/bpf/20260611115503.AC16D1F00893@smtp.kernel.org/
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/trace/bpf_trace.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 82f8feea6931..75495a5c3507 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2376,9 +2376,12 @@ static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32
 	int err = -ENOMEM;
 	unsigned int i;
 
+	if (!access_ok(usyms, cnt * sizeof(*usyms)))
+		return -EFAULT;
+
 	syms = kvmalloc_array(cnt, sizeof(*syms), GFP_KERNEL);
 	if (!syms)
-		goto error;
+		return -ENOMEM;
 
 	buf = kvmalloc_array(cnt, KSYM_NAME_LEN, GFP_KERNEL);
 	if (!buf)
@@ -2403,10 +2406,8 @@ static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32
 	return 0;
 
 error:
-	if (err) {
-		kvfree(syms);
-		kvfree(buf);
-	}
+	kvfree(syms);
+	kvfree(buf);
 	return err;
 }
 
-- 
2.54.0