[lxc-devel] [lxd/master] forkexec: tweak

[brauner on Github]

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From ea97c203053b51e3a1989e958a89c4df046b38dc Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Sun, 29 Mar 2020 13:27:26 +0200
Subject: [PATCH] forkexec: tweak

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 lxd/include/macro.h  | 13 ++++++++++
 lxd/main_forkexec.go | 57 +++++++++++++++++++-------------------------
 2 files changed, 38 insertions(+), 32 deletions(-)

diff --git a/lxd/include/macro.h b/lxd/include/macro.h
index 7ff60c385d..ece46bc2c7 100644
--- a/lxd/include/macro.h
+++ b/lxd/include/macro.h
@@ -255,4 +255,17 @@ enum {
 		__internal_fd__;            \
 	})
 
+#define ret_errno(__errno__)         \
+	({                           \
+		errno = (__errno__); \
+		-(__errno__);        \
+	})
+
+#define log_error(__ret__, format, ...)                       \
+	({                                                    \
+		typeof(__ret__) __internal_ret__ = (__ret__); \
+		fprintf(stderr, format "\n", ##__VA_ARGS__);  \
+		__internal_ret__;                             \
+	})
+
 #endif /* __LXC_MACRO_H */
diff --git a/lxd/main_forkexec.go b/lxd/main_forkexec.go
index 6bc60daf3e..f63fce0eb6 100644
--- a/lxd/main_forkexec.go
+++ b/lxd/main_forkexec.go
@@ -22,6 +22,7 @@ import (
 #include <unistd.h>
 #include <limits.h>
 
+#include "include/macro.h"
 #include "include/memory_utils.h"
 #include <lxc/attach_options.h>
 #include <lxc/lxccontainer.h>
@@ -63,52 +64,40 @@ again:
 	return status;
 }
 
-static char *must_copy_string(const char *entry)
-{
-	char *ret;
-
-	if (!entry)
-		return NULL;
-
-	do {
-		ret = strdup(entry);
-	} while (!ret);
-
-	return ret;
-}
-
-static void *must_realloc(void *orig, size_t sz)
-{
-	void *ret;
-
-	do {
-		ret = realloc(orig, sz);
-	} while (!ret);
-
-	return ret;
-}
-
 static int append_null_to_list(void ***list)
 {
 	int newentry = 0;
+	void **new_list;
 
 	if (*list)
 		for (; (*list)[newentry]; newentry++)
 			;
 
-	*list = must_realloc(*list, (newentry + 2) * sizeof(void **));
+	new_list = realloc(*list, (newentry + 2) * sizeof(void **));
+	if (!new_list)
+		return ret_errno(ENOMEM);
+
+	*list = new_list;
 	(*list)[newentry + 1] = NULL;
 	return newentry;
 }
 
-static void must_append_string(char ***list, char *entry)
+static int push_vargs(char ***list, char *entry)
 {
+	__do_free char *copy = NULL;
 	int newentry;
-	char *copy;
+
+	copy = strdup(entry);
+	if (!copy)
+		return ret_errno(ENOMEM);
 
 	newentry = append_null_to_list((void ***)list);
-	copy = must_copy_string(entry);
-	(*list)[newentry] = copy;
+	if (newentry < 0)
+		return newentry;
+
+	(*list)[newentry] = move_ptr(copy);
+
+	return 0;
 }
 
 // We use a separate function because cleanup macros are called during stack
@@ -167,9 +156,13 @@ __attribute__ ((noinline)) static int __forkexec(void)
 		if (!strcmp(section, "env")) {
 			if (!strncmp(arg, "HOME=", STRLITERALLEN("HOME=")))
 				attach_options.initial_cwd = arg + STRLITERALLEN("HOME=");
-			must_append_string(&envvp, arg);
+			ret = push_vargs(&envvp, arg);
+			if (ret < 0)
+				return log_error(ret, "Failed to add %s to env array", arg);
 		} else if (!strcmp(section, "cmd")) {
-			must_append_string(&argvp, arg);
+			ret = push_vargs(&argvp, arg);
+			if (ret < 0)
+				return log_error(ret, "Failed to add %s to arg array", arg);
 		} else {
 			fprintf(stderr, "Invalid exec section %s\n", section);
 			return EXIT_FAILURE;