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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2013-07-23 22:06:15 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-08-29 09:47:32 -0700
commit29632b10ef02a31dec2918177f6d4244e66d635d (patch)
tree5890cb1d61bfda1845241d6891516ef86041c79c
parent7272711a2fc64dd6ef980630e129d8731897ee56 (diff)
downloadvexpress-lsk-29632b10ef02a31dec2918177f6d4244e66d635d.tar.gz
ftrace: Add check for NULL regs if ops has SAVE_REGS set
commit 195a8afc7ac962f8da795549fe38e825f1372b0d upstream. If a ftrace ops is registered with the SAVE_REGS flag set, and there's already a ops registered to one of its functions but without the SAVE_REGS flag, there's a small race window where the SAVE_REGS ops gets added to the list of callbacks to call for that function before the callback trampoline gets set to save the regs. The problem is, the function is not currently saving regs, which opens a small race window where the ops that is expecting regs to be passed to it, wont. This can cause a crash if the callback were to reference the regs, as the SAVE_REGS guarantees that regs will be set. To fix this, we add a check in the loop case where it checks if the ops has the SAVE_REGS flag set, and if so, it will ignore it if regs is not set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/trace/ftrace.c18
1 files changed, 14 insertions, 4 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 6c508ff33c6..13f12351b35 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1416,12 +1416,22 @@ ftrace_hash_move(struct ftrace_ops *ops, int enable,
* the hashes are freed with call_rcu_sched().
*/
static int
-ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip)
+ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip, void *regs)
{
struct ftrace_hash *filter_hash;
struct ftrace_hash *notrace_hash;
int ret;
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ /*
+ * There's a small race when adding ops that the ftrace handler
+ * that wants regs, may be called without them. We can not
+ * allow that handler to be called if regs is NULL.
+ */
+ if (regs == NULL && (ops->flags & FTRACE_OPS_FL_SAVE_REGS))
+ return 0;
+#endif
+
filter_hash = rcu_dereference_raw_notrace(ops->filter_hash);
notrace_hash = rcu_dereference_raw_notrace(ops->notrace_hash);
@@ -4188,7 +4198,7 @@ static inline void ftrace_startup_enable(int command) { }
# define ftrace_shutdown_sysctl() do { } while (0)
static inline int
-ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip)
+ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip, void *regs)
{
return 1;
}
@@ -4211,7 +4221,7 @@ ftrace_ops_control_func(unsigned long ip, unsigned long parent_ip,
do_for_each_ftrace_op(op, ftrace_control_list) {
if (!(op->flags & FTRACE_OPS_FL_STUB) &&
!ftrace_function_local_disabled(op) &&
- ftrace_ops_test(op, ip))
+ ftrace_ops_test(op, ip, regs))
op->func(ip, parent_ip, op, regs);
} while_for_each_ftrace_op(op);
trace_recursion_clear(TRACE_CONTROL_BIT);
@@ -4244,7 +4254,7 @@ __ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
*/
preempt_disable_notrace();
do_for_each_ftrace_op(op, ftrace_ops_list) {
- if (ftrace_ops_test(op, ip))
+ if (ftrace_ops_test(op, ip, regs))
op->func(ip, parent_ip, op, regs);
} while_for_each_ftrace_op(op);
preempt_enable_notrace();