Merge tag 'trace-v5.0-rc4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

torvalds · torvalds · commit 10f490217313 · 2019-02-18T09:40:16.000-08:00
Pull tracing fixes from Steven Rostedt:
 "Two more tracing fixes

   - Have kprobes not use copy_from_user() to access kernel addresses,
     because kprobes can legitimately poke at bad kernel memory, which
     will fault. Copy from user code should never fault in kernel space.
     Using probe_mem_read() can handle kernel address space faulting.

   - Put back the entries counter in the tracing output that was
     accidentally removed"

* tag 'trace-v5.0-rc4-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Fix number of entries in trace header
  kprobe: Do not use uaccess functions to access kernel memory that can fault
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
@@ -3384,6 +3384,8 @@ static void print_func_help_header_irq(struct trace_buffer *buf, struct seq_file
 	const char tgid_space[] = "          ";
 	const char space[] = "  ";
 
+	print_event_info(buf, m);
+
 	seq_printf(m, "#                          %s  _-----=> irqs-off\n",
 		   tgid ? tgid_space : space);
 	seq_printf(m, "#                          %s / _----=> need-resched\n",
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
@@ -861,22 +861,14 @@ static const struct file_operations kprobe_profile_ops = {
 static nokprobe_inline int
 fetch_store_strlen(unsigned long addr)
 {
-	mm_segment_t old_fs;
 	int ret, len = 0;
 	u8 c;
 
-	old_fs = get_fs();
-	set_fs(KERNEL_DS);
-	pagefault_disable();
-
 	do {
-		ret = __copy_from_user_inatomic(&c, (u8 *)addr + len, 1);
+		ret = probe_mem_read(&c, (u8 *)addr + len, 1);
 		len++;
 	} while (c && ret == 0 && len < MAX_STRING_SIZE);
 
-	pagefault_enable();
-	set_fs(old_fs);
-
 	return (ret < 0) ? ret : len;
 }
 
