From: Qiujun Huang hqjagain@gmail.com
The nesting count of trace_printk allows for 4 levels of nesting. The nesting counter starts at zero and is incremented before being used to retrieve the current context's buffer. But the index to the buffer uses the nesting counter after it was incremented, and not its original number, which in needs to do.
Link: https://lkml.kernel.org/r/20201029161905.4269-1-hqjagain@gmail.com
Cc: stable@vger.kernel.org Fixes: 3d9622c12c887 ("tracing: Add barrier to trace_printk() buffer nesting modification") Signed-off-by: Qiujun Huang hqjagain@gmail.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org --- kernel/trace/trace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 528971714fc6..daa96215e294 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3132,7 +3132,7 @@ static char *get_trace_buf(void)
/* Interrupts must see nesting incremented before we use the buffer */ barrier(); - return &buffer->buffer[buffer->nesting][0]; + return &buffer->buffer[buffer->nesting - 1][0]; }
static void put_trace_buf(void)