Commit 27527410 authored by Ze Gao's avatar Ze Gao Committed by Masami Hiramatsu (Google)
Browse files

fprobe: add recursion detection in fprobe_exit_handler 

fprobe_hander and fprobe_kprobe_handler has guarded ftrace recursion
detection but fprobe_exit_handler has not, which possibly introduce
recursive 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 recursion free guard the same way as fprobe_hander. Since
ftrace recursion check does not employ ip(s), so here use entry_ip and
entry_parent_ip the same as fprobe_handler.

Link: https://lore.kernel.org/all/20230517034510.15639-4-zegao@tencent.com/



Fixes: 5b0ab789 ("fprobe: Add exit_handler support")
Signed-off-by: default avatarZe Gao <zegao@tencent.com>
Cc: stable@vger.kernel.org
Acked-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
parent 3cc4e2c5

kernel/trace/fprobe.c

+14 −0
Original line number Diff line number Diff line
@@ -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 void __fprobe_handler(unsigned long ip, unsigned long parent_ip, 
		}

		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;

	}
@@ -114,14 +116,26 @@ static void fprobe_exit_handler(struct rethook_node *rh, void *data, 
{

	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);