bpf:bpf_seq_printf(): handle potentially unsafe format string better

User the proper helper for kernel or userspace addresses based on
TASK_SIZE instead of the dangerous strncpy_from_unsafe function.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index a2efbda..deefe28 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -588,15 +588,17 @@ BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size,
                }
 
                if (fmt[i] == 's') {
+                       void *unsafe_ptr;
+
                        /* try our best to copy */
                        if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) {
                                err = -E2BIG;
                                goto out;
                        }
 
-                       err = strncpy_from_unsafe_strict(bufs->buf[memcpy_cnt],
-                                                        (void *) (long) args[fmt_cnt],
-                                                        MAX_SEQ_PRINTF_STR_LEN);
+                       unsafe_ptr = (void *)(long)args[fmt_cnt];
+                       err = strncpy_from_kernel_nofault(bufs->buf[memcpy_cnt],
+                                       unsafe_ptr, MAX_SEQ_PRINTF_STR_LEN);
                        if (err < 0)
                                bufs->buf[memcpy_cnt][0] = '\0';
                        params[fmt_cnt] = (u64)(long)bufs->buf[memcpy_cnt];