From b518a50dd136bcaef2ad5988c1fe53f954d5ae5e Mon Sep 17 00:00:00 2001
From: kevans <kevans@FreeBSD.org>
Date: Sat, 7 Nov 2020 03:28:32 +0000
Subject: [PATCH] imgact_binmisc: minor re-organization of imgact_binmisc_exec
 exits

Notably, streamline error paths through the existing 'done' label, making it
easier to quickly verify correct cleanup.

Future work might add a kernel-only flag to indicate that a interpreter uses
#a. Currently, all executions via imgact_binmisc pay the penalty of
constructing sname/fname, even if they will not use it. qemu-user-static
doesn't need it, the stock rc script for qemu-user-static certainly doesn't
use it, and I suspect these are the vast majority of (if not the only)
current users.

MFC after:	1 week
---
 sys/kern/imgact_binmisc.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/sys/kern/imgact_binmisc.c b/sys/kern/imgact_binmisc.c
index 082dd3076b5e..af8f78cee59b 100644
--- a/sys/kern/imgact_binmisc.c
+++ b/sys/kern/imgact_binmisc.c
@@ -580,24 +580,24 @@ imgact_binmisc_exec(struct image_params *imgp)
 	struct sbuf *sname;
 	char *s, *d;
 
+	sname = NULL;
 	/* Do we have an interpreter for the given image header? */
 	sx_slock(&interp_list_sx);
 	if ((ibe = imgact_binmisc_find_interpreter(image_header)) == NULL) {
-		sx_sunlock(&interp_list_sx);
-		return (-1);
+		error = -1;
+		goto done;
 	}
 
 	/* No interpreter nesting allowed. */
 	if (imgp->interpreted & IMGACT_BINMISC) {
-		sx_sunlock(&interp_list_sx);
-		return (ENOEXEC);
+		error = ENOEXEC;
+		goto done;
 	}
 
 	imgp->interpreted |= IMGACT_BINMISC;
 
 	if (imgp->args->fname != NULL) {
 		fname = imgp->args->fname;
-		sname = NULL;
 	} else {
 		/* Use the fdescfs(5) path for fexecve(2). */
 		sname = sbuf_new_auto();
@@ -636,7 +636,6 @@ imgact_binmisc_exec(struct image_params *imgp)
 
 		default:
 			/* Hmm... This shouldn't happen. */
-			sx_sunlock(&interp_list_sx);
 			printf("%s: Unknown macro #%c sequence in "
 			    "interpreter string\n", KMOD_NAME, *(s + 1));
 			error = EINVAL;
@@ -648,7 +647,6 @@ imgact_binmisc_exec(struct image_params *imgp)
 	/* Make room for the interpreter */
 	error = exec_args_adjust_args(imgp->args, 0, offset);
 	if (error != 0) {
-		sx_sunlock(&interp_list_sx);
 		goto done;
 	}
 
@@ -698,11 +696,11 @@ imgact_binmisc_exec(struct image_params *imgp)
 		s++;
 	}
 	*d = '\0';
-	sx_sunlock(&interp_list_sx);
 
 	imgp->interpreter_name = imgp->args->begin_argv;
 
 done:
+	sx_sunlock(&interp_list_sx);
 	if (sname)
 		sbuf_delete(sname);
 	return (error);