[PATCH 3.10 03/79] tracing: Check if tracing is enabled in trace_puts()

From: Greg Kroah-Hartman
Date: Tue Feb 11 2014 - 14:43:57 EST


3.10-stable review patch. If anyone has any objections, please let me know.

------------------

From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>

commit 3132e107d608f8753240d82d61303c500fd515b4 upstream.

If trace_puts() is used very early in boot up, it can crash the machine
if it is called before the ring buffer is allocated. If a trace_printk()
is used with no arguments, then it will be converted into a trace_puts()
and suffer the same fate.

Fixes: 09ae72348ecc "tracing: Add trace_puts() for even faster trace_printk() tracing"
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
kernel/trace/trace.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -424,6 +424,9 @@ int __trace_puts(unsigned long ip, const
unsigned long irq_flags;
int alloc;

+ if (unlikely(tracing_selftest_running || tracing_disabled))
+ return 0;
+
alloc = sizeof(*entry) + size + 2; /* possible \n added */

local_save_flags(irq_flags);
@@ -464,6 +467,9 @@ int __trace_bputs(unsigned long ip, cons
unsigned long irq_flags;
int size = sizeof(struct bputs_entry);

+ if (unlikely(tracing_selftest_running || tracing_disabled))
+ return 0;
+
local_save_flags(irq_flags);
buffer = global_trace.trace_buffer.buffer;
event = trace_buffer_lock_reserve(buffer, TRACE_BPUTS, size,


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