[PATCH] tracing: Check result of ring_buffer_read_prepare()

From: Namhyung Kim
Date: Tue Apr 09 2013 - 21:55:47 EST


From: Namhyung Kim <namhyung.kim@xxxxxxx>

The ring_buffer_read_prepare() can return NULL if memory allocation
fails. Fail out in this case instead of succedding and then having
no output.

Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
kernel/trace/trace.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7270460cfe3c..13200de31f0b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2826,6 +2826,8 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
for_each_tracing_cpu(cpu) {
iter->buffer_iter[cpu] =
ring_buffer_read_prepare(iter->trace_buffer->buffer, cpu);
+ if (!iter->buffer_iter[cpu])
+ goto free;
}
ring_buffer_read_prepare_sync();
for_each_tracing_cpu(cpu) {
@@ -2836,6 +2838,9 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
cpu = iter->cpu_file;
iter->buffer_iter[cpu] =
ring_buffer_read_prepare(iter->trace_buffer->buffer, cpu);
+ if (!iter->buffer_iter[cpu])
+ goto free;
+
ring_buffer_read_prepare_sync();
ring_buffer_read_start(iter->buffer_iter[cpu]);
tracing_iter_reset(iter, cpu);
@@ -2847,6 +2852,23 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)

return iter;

+free:
+ /*
+ * For simplicity, just keep single loop without comparing cpu_file.
+ */
+ for_each_tracing_cpu(cpu) {
+ if (iter->buffer_iter[cpu])
+ ring_buffer_read_finish(iter->buffer_iter[cpu]);
+ }
+
+ if (iter->trace && iter->trace->close)
+ iter->trace->close(iter);
+
+ if (!iter->snapshot)
+ tracing_start_tr(tr);
+
+ mutex_destroy(&iter->mutex);
+ free_cpumask_var(iter->started);
fail:
mutex_unlock(&trace_types_lock);
kfree(iter->trace);
--
1.7.11.7

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