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[for-linus,1/3] tracing: Fix out of bounds write in get_trace_buf

Message ID 20201031130931.062903467@goodmis.org
State Accepted
Commit c1acb4ac1a892cf08d27efcb964ad281728b0545
Headers show
Series [for-linus,1/3] tracing: Fix out of bounds write in get_trace_buf | expand

Commit Message

Steven Rostedt Oct. 31, 2020, 1:06 p.m. UTC 
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(-)
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Patch

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)