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ring-buffer: Check if buffer exists before polling

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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>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2014-06-10 09:46:00 -04:00 committed by Steven Rostedt
parent a9fcaaac37
commit 8b8b36834d
3 changed files with 21 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/ring_buffer.h
View File

@ -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);

5
kernel/trace/ring_buffer.c
View File

@ -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;
}
/**

22
kernel/trace/trace.c
View File

@ -1085,13 +1085,13 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
}
#endif /* CONFIG_TRACER_MAX_TRACE */
static void wait_on_pipe(struct trace_iterator *iter)
static int wait_on_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
@ -4378,6 +4378,7 @@ tracing_poll_pipe(struct file *filp, poll_table *poll_table)
static int tracing_wait_pipe(struct file *filp)
{
struct trace_iterator *iter = filp->private_data;
int ret;
while (trace_empty(iter)) {
@ -4399,10 +4400,13 @@ static int tracing_wait_pipe(struct file *filp)
mutex_unlock(&iter->mutex);
wait_on_pipe(iter);
ret = wait_on_pipe(iter);
mutex_lock(&iter->mutex);
if (ret)
return ret;
if (signal_pending(current))
return -EINTR;
}
@ -5327,8 +5331,12 @@ tracing_buffers_read(struct file *filp, char __user *ubuf,
goto out_unlock;
}
mutex_unlock(&trace_types_lock);
wait_on_pipe(iter);
ret = wait_on_pipe(iter);
mutex_lock(&trace_types_lock);
if (ret) {
size = ret;
goto out_unlock;
}
if (signal_pending(current)) {
size = -EINTR;
goto out_unlock;
@ -5538,8 +5546,10 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
goto out;
}
mutex_unlock(&trace_types_lock);
wait_on_pipe(iter);
ret = wait_on_pipe(iter);
mutex_lock(&trace_types_lock);
if (ret)
goto out;
if (signal_pending(current)) {
ret = -EINTR;
goto out;