ring-buffer: Check if buffer exists before polling

commit 8b8b36834d0fff67fc8668093f4312dd04dcf21d upstream.

The per_cpu buffers are created one per possible CPU. But these do
not mean that those CPUs are online, nor do they even exist.

With the addition of the ring buffer polling, it assumes that the
caller polls on an existing buffer. But this is not the case if
the user reads trace_pipe from a CPU that does not exist, and this
causes the kernel to crash.

Simple fix is to check the cpu against buffer bitmask against to see
if the buffer was allocated or not and return -ENODEV if it is
not.

More updates were done to pass the -ENODEV back up to userspace.

Link: http://lkml.kernel.org/r/5393DB61.6060707@oracle.com
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index d69cf637a15a3093863cd33f09929b87d73fd0a9..49a4d6f59108f957d4534190c161344981c48e46 100644 (file)
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -97,7 +97,7 @@ __ring_buffer_alloc(unsigned long size, unsigned flags, struct lock_class_key *k
        __ring_buffer_alloc((size), (flags), &__key);   \
 })
 
-void ring_buffer_wait(struct ring_buffer *buffer, int cpu);
+int ring_buffer_wait(struct ring_buffer *buffer, int cpu);
 int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
                          struct file *filp, poll_table *poll_table);
 

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index fd12cc56371f1a17caf18c80fd157fb16608711a..8e94c1102636670dabf637e5aff3e2e65fa661bc 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -543,7 +543,7 @@ static void rb_wake_up_waiters(struct irq_work *work)
  * as data is added to any of the @buffer's cpu buffers. Otherwise
  * it will wait for data to be added to a specific cpu buffer.
  */
-void ring_buffer_wait(struct ring_buffer *buffer, int cpu)
+int ring_buffer_wait(struct ring_buffer *buffer, int cpu)
 {
        struct ring_buffer_per_cpu *cpu_buffer;
        DEFINE_WAIT(wait);
@@ -557,6 +557,8 @@ void ring_buffer_wait(struct ring_buffer *buffer, int cpu)
        if (cpu == RING_BUFFER_ALL_CPUS)
                work = &buffer->irq_work;
        else {
+               if (!cpumask_test_cpu(cpu, buffer->cpumask))
+                       return -ENODEV;
                cpu_buffer = buffer->buffers[cpu];
                work = &cpu_buffer->irq_work;
        }
@@ -591,6 +593,7 @@ void ring_buffer_wait(struct ring_buffer *buffer, int cpu)
                schedule();
 
        finish_wait(&work->waiters, &wait);
+       return 0;
 }
 
 /**

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 21920add7972c40562e73efb48535d4b7ba36b84..8fe92ce43f39fc7a85b5c937533e22a089e6a56f 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1027,13 +1027,13 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 }
 #endif /* CONFIG_TRACER_MAX_TRACE */
 
-static void default_wait_pipe(struct trace_iterator *iter)
+static int default_wait_pipe(struct trace_iterator *iter)
 {
        /* Iterators are static, they should be filled or empty */
        if (trace_buffer_iter(iter, iter->cpu_file))
-               return;
+               return 0;
 
-       ring_buffer_wait(iter->trace_buffer->buffer, iter->cpu_file);
+       return ring_buffer_wait(iter->trace_buffer->buffer, iter->cpu_file);
 }
 
 #ifdef CONFIG_FTRACE_STARTUP_TEST
@@ -4054,17 +4054,19 @@ tracing_poll_pipe(struct file *filp, poll_table *poll_table)
  *
  *     Anyway, this is really very primitive wakeup.
  */
-void poll_wait_pipe(struct trace_iterator *iter)
+int poll_wait_pipe(struct trace_iterator *iter)
 {
        set_current_state(TASK_INTERRUPTIBLE);
        /* sleep for 100 msecs, and try again. */
        schedule_timeout(HZ / 10);
+       return 0;
 }
 
 /* Must be called with trace_types_lock mutex held. */
 static int tracing_wait_pipe(struct file *filp)
 {
        struct trace_iterator *iter = filp->private_data;
+       int ret;
 
        while (trace_empty(iter)) {
 
@@ -4074,10 +4076,13 @@ static int tracing_wait_pipe(struct file *filp)
 
                mutex_unlock(&iter->mutex);
 
-               iter->trace->wait_pipe(iter);
+               ret = iter->trace->wait_pipe(iter);
 
                mutex_lock(&iter->mutex);
 
+               if (ret)
+                       return ret;
+
                if (signal_pending(current))
                        return -EINTR;
 
@@ -5011,8 +5016,12 @@ tracing_buffers_read(struct file *filp, char __user *ubuf,
                                goto out_unlock;
                        }
                        mutex_unlock(&trace_types_lock);
-                       iter->trace->wait_pipe(iter);
+                       ret = iter->trace->wait_pipe(iter);
                        mutex_lock(&trace_types_lock);
+                       if (ret) {
+                               size = ret;
+                               goto out_unlock;
+                       }
                        if (signal_pending(current)) {
                                size = -EINTR;
                                goto out_unlock;
@@ -5224,8 +5233,10 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
                        goto out;
                }
                mutex_unlock(&trace_types_lock);
-               iter->trace->wait_pipe(iter);
+               ret = iter->trace->wait_pipe(iter);
                mutex_lock(&trace_types_lock);
+               if (ret)
+                       goto out;
                if (signal_pending(current)) {
                        ret = -EINTR;
                        goto out;

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 51b44483eb78b87f21c263a4868288284bc10b74..aa0e736b72ac84d77a633ab8c83f8d1378883147 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -342,7 +342,7 @@ struct tracer {
        void                    (*stop)(struct trace_array *tr);
        void                    (*open)(struct trace_iterator *iter);
        void                    (*pipe_open)(struct trace_iterator *iter);
-       void                    (*wait_pipe)(struct trace_iterator *iter);
+       int                     (*wait_pipe)(struct trace_iterator *iter);
        void                    (*close)(struct trace_iterator *iter);
        void                    (*pipe_close)(struct trace_iterator *iter);
        ssize_t                 (*read)(struct trace_iterator *iter,
@@ -557,7 +557,7 @@ void trace_init_global_iter(struct trace_iterator *iter);
 
 void tracing_iter_reset(struct trace_iterator *iter, int cpu);
 
-void poll_wait_pipe(struct trace_iterator *iter);
+int poll_wait_pipe(struct trace_iterator *iter);
 
 void ftrace(struct trace_array *tr,
                            struct trace_array_cpu *data,