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tracing: Add NULL checks for buffer in ring_buffer_free_read_page()

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In a previous commit 7433632c9f, buffer, buffer->buffers and
buffer->buffers[cpu] in ring_buffer_wake_waiters() can be NULL,
and thus the related checks are added.

However, in the same call stack, these variables are also used in
ring_buffer_free_read_page():

tracing_buffers_release()
  ring_buffer_wake_waiters(iter->array_buffer->buffer)
    cpu_buffer = buffer->buffers[cpu] -> Add checks by previous commit
  ring_buffer_free_read_page(iter->array_buffer->buffer)
    cpu_buffer = buffer->buffers[cpu] -> No check

Thus, to avod possible null-pointer derefernces, the related checks
should be added.

These results are reported by a static tool designed by myself.

Link: https://lkml.kernel.org/r/20230113125501.760324-1-baijiaju1990@gmail.com

Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Jia-Ju Bai 2023-01-13 20:55:01 +08:00 committed by Steven Rostedt (Google)
parent b56c68f705
commit 3e4272b995
1 changed files with 6 additions and 1 deletions
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7
kernel/trace/ring_buffer.c
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@ -5626,11 +5626,16 @@ EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
*/
void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
struct ring_buffer_per_cpu *cpu_buffer;
struct buffer_data_page *bpage = data;
struct page *page = virt_to_page(bpage);
unsigned long flags;
if (!buffer || !buffer->buffers || !buffer->buffers[cpu])
return;
cpu_buffer = buffer->buffers[cpu];
/* If the page is still in use someplace else, we can't reuse it */
if (page_ref_count(page) > 1)
goto out;