diff mbox series

[3/4] fprobe: add recursion detection in fprobe_exit_handler

Message ID 20230515031314.7836-4-zegao@tencent.com
State New
Headers
Series [1/4] rethook: use preempt_{disable, enable}_notrace in rethook_trampoline_handler |

Commit Message

Ze Gao May 15, 2023, 3:13 a.m. UTC 
  fprobe_hander and fprobe_kprobe_handler has guarded ftrace recusion
detection but fprobe_exit_handler has not, which possibly introduce
recurive calls if the fprobe exit callback calls any traceable
functions. Checking in fprobe_hander or fprobe_kprobe_handler
is not enough and misses this case.

So add recusion free guard the same way as fprobe_hander and also
mark fprobe_exit_handler notrace. Since ftrace recursion check does
not employ ips, so here use entry_ip and entry_parent_ip the same as
fprobe_handler.

Signed-off-by: Ze Gao <zegao@tencent.com>
---
 kernel/trace/fprobe.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index ad9a36c87ad9..cf982d4ab142 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -17,6 +17,7 @@ 
 struct fprobe_rethook_node {
 	struct rethook_node node;
 	unsigned long entry_ip;
+	unsigned long entry_parent_ip;
 	char data[];
 };
 
@@ -39,6 +40,7 @@  static inline notrace void __fprobe_handler(unsigned long ip, unsigned long
 		}
 		fpr = container_of(rh, struct fprobe_rethook_node, node);
 		fpr->entry_ip = ip;
+		fpr->entry_parent_ip = parent_ip;
 		if (fp->entry_data_size)
 			entry_data = fpr->data;
 	}
@@ -109,19 +111,30 @@  static void notrace fprobe_kprobe_handler(unsigned long ip, unsigned long parent
 	ftrace_test_recursion_unlock(bit);
 }
 
-static void fprobe_exit_handler(struct rethook_node *rh, void *data,
+static void notrace fprobe_exit_handler(struct rethook_node *rh, void *data,
 				struct pt_regs *regs)
 {
 	struct fprobe *fp = (struct fprobe *)data;
 	struct fprobe_rethook_node *fpr;
+	int bit;
 
 	if (!fp || fprobe_disabled(fp))
 		return;
 
 	fpr = container_of(rh, struct fprobe_rethook_node, node);
 
+	/* we need to assure no calls to traceable functions in-between the
+	 * end of fprobe_handler and the beginning of fprobe_exit_handler.
+	 */
+	bit = ftrace_test_recursion_trylock(fpr->entry_ip, fpr->entry_parent_ip);
+	if (bit < 0) {
+		fp->nmissed++;
+		return;
+	}
+
 	fp->exit_handler(fp, fpr->entry_ip, regs,
 			 fp->entry_data_size ? (void *)fpr->data : NULL);
+	ftrace_test_recursion_unlock(bit);
 }
 NOKPROBE_SYMBOL(fprobe_exit_handler);