tracing: eval_map_next() should always increase position index

if seq_file .next fuction does not change position index, read after some lseek can generate unexpected output. Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Vasily Averin <[email protected]> [ This is not a bug fix, it just makes it "technically correct" which is why I applied it. NULL is only returned on an anomaly which triggers a WARN_ON ] Signed-off-by: Steven Rostedt (VMware) <[email protected]>
jbg · Jan 30, 2020 · 039958a · 039958a
1 parent e4075e8
commit 039958a
Showing 1 changed file with 1 addition and 3 deletions.
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
@@ -5399,14 +5399,12 @@ static void *eval_map_next(struct seq_file *m, void *v, loff_t *pos)
 	 * Paranoid! If ptr points to end, we don't want to increment past it.
 	 * This really should never happen.
 	 */
+	(*pos)++;
 	ptr = update_eval_map(ptr);
 	if (WARN_ON_ONCE(!ptr))
 		return NULL;
 
 	ptr++;
-
-	(*pos)++;
-
 	ptr = update_eval_map(ptr);
 
 	return ptr;