From: Jia-Ju Bai <baijiaju1990@xxxxxxxxx> [ Upstream commit 3e4272b9954094907f16861199728f14002fcaf6 ] In a previous commit 7433632c9ff6, 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@xxxxxxxxx Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx> Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/trace/ring_buffer.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 999dae39f12e5..a7808f8b6f56a 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -4554,11 +4554,16 @@ EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); */ void ring_buffer_free_read_page(struct ring_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; -- 2.39.2