From: Qiujun Huang hqjagain@gmail.com
stable inclusion from linux-4.19.156 commit 7e4eeff7da1df5602e9af340d01b2ce1b4662d3e
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commit c1acb4ac1a892cf08d27efcb964ad281728b0545 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- 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 e32aae03f6be..b4f429106ad4 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2817,7 +2817,7 @@ 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)