[PATCH] tracing: Fix tracing buffer length in tracing_mark_write

[Wang ShaoBo]

__copy_from_user_inatomic() return the byte length that copied failed,
tracing buffer should left this bytes.
Fixes: 656c7f0d2d2b ("tracing: Replace kmap with copy_from_user() in 
trace_marker writing")
Signed-off-by: Wang ShaoBo <bobo.shaobow...@huawei.com>
---
 kernel/trace/trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 29615f15a820..ed5fe0f165e0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6628,7 +6628,7 @@ tracing_mark_write(struct file *filp, const char __user 
*ubuf,
                written = -EFAULT;
        } else
                written = cnt;
-       len = cnt;
+       cnt -= len;
 
        if (tr->trace_marker_file && 
!list_empty(&tr->trace_marker_file->triggers)) {
                /* do not add \n before testing triggers, but add \0 */
-- 
2.17.1