tracing: Do not risk busy looping in buffer splice

If the read loop in trace_buffers_splice_read() keeps failing due to
memory allocation failures without reading even a single page then this
function will keep busy looping.

Remove the risk for that by exiting the function if memory allocation
failures are seen.

Link: http://lkml.kernel.org/r/1415309167-2373-2-git-send-email-rabin@rab.in

Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 15209335888d..92f4a6cee172 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5494,7 +5494,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
         };
         struct buffer_ref *ref;
         int entries, size, i;
-        ssize_t ret;
+        ssize_t ret = 0;
 
         mutex_lock(&trace_types_lock);
 
@@ -5532,13 +5532,16 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
                 int r;
 
                 ref = kzalloc(sizeof(*ref), GFP_KERNEL);
-                if (!ref)
+                if (!ref) {
+                        ret = -ENOMEM;
                         break;
+                }
 
                 ref->ref = 1;
                 ref->buffer = iter->trace_buffer->buffer;
                 ref->page = ring_buffer_alloc_read_page(ref->buffer, iter->cpu_file);
                 if (!ref->page) {
+                        ret = -ENOMEM;
                         kfree(ref);
                         break;
                 }
@@ -5576,6 +5579,9 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 
         /* did we read anything? */
         if (!spd.nr_pages) {
+                if (ret)
+                        goto out;
+
                 if ((file->f_flags & O_NONBLOCK) || (flags & SPLICE_F_NONBLOCK)) {
                         ret = -EAGAIN;
                         goto out;