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>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 15209335888db6c6087fcf4178e36a9aed278499..92f4a6cee1727360ff9d739a126f168a6cacd980 100644 (file)
--- 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;