From a98b21a035844bed64eff8c9a0174d21179c085f Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Fri, 29 Jan 2021 11:31:53 +0100
Subject: [PATCH] attach: fix personality handling

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
 src/lxc/attach.c         | 33 ++++++++++++++++++++++-----------
 src/lxc/attach_options.h |  2 +-
 src/lxc/confile.c        |  2 +-
 src/lxc/confile.h        |  7 ++++++-
 4 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/src/lxc/attach.c b/src/lxc/attach.c
index 9ad7a56d8e..f66f65a5ba 100644
--- a/src/lxc/attach.c
+++ b/src/lxc/attach.c
@@ -71,15 +71,24 @@ static struct attach_context *alloc_attach_context(void)
 	return zalloc(sizeof(struct attach_context));
 }
 
-static signed long get_personality(const char *name, const char *lxcpath)
+static int get_personality(const char *name, const char *lxcpath,
+			   signed long *personality)
 {
 	__do_free char *p = NULL;
+	signed long per;
 
 	p = lxc_cmd_get_config_item(name, "lxc.arch", lxcpath);
-	if (!p)
-		return -1;
+	if (!p) {
+		*personality = LXC_ARCH_UNCHANGED;
+		return 0;
+	}
+
+	per = lxc_config_parse_arch(p);
+	if (per == LXC_ARCH_UNCHANGED)
+		return ret_errno(EINVAL);
 
-	return lxc_config_parse_arch(p);
+	*personality = per;
+	return 0;
 }
 
 static int get_attach_context(struct attach_context *ctx,
@@ -127,9 +136,9 @@ static int get_attach_context(struct attach_context *ctx,
 	for (int i = 0; i < LXC_NS_MAX; i++)
 		ctx->ns_fd[i] = -EBADF;
 
-	ctx->personality = get_personality(container->name, container->config_path);
-	if (ctx->personality < 0)
-		return log_error_errno(-ENOENT, ENOENT, "Failed to get personality of the container");
+	ret = get_personality(container->name, container->config_path, &ctx->personality);
+	if (ret)
+		return log_error_errno(ret, errno, "Failed to get personality of the container");
 
 	if (!ctx->container->lxc_conf) {
 		ctx->container->lxc_conf = lxc_conf_init();
@@ -751,11 +760,13 @@ __noreturn static void do_attach(struct attach_clone_payload *payload)
 		else
 			new_personality = options->personality;
 
-		ret = personality(new_personality);
-		if (ret < 0)
-			goto on_error;
+		if (new_personality != LXC_ARCH_UNCHANGED) {
+			ret = personality(new_personality);
+			if (ret < 0)
+				goto on_error;
 
-		TRACE("Set new personality");
+			TRACE("Set new personality");
+		}
 	}
 #endif
 
diff --git a/src/lxc/attach_options.h b/src/lxc/attach_options.h
index 80fe439103..3a596fb305 100644
--- a/src/lxc/attach_options.h
+++ b/src/lxc/attach_options.h
@@ -124,7 +124,7 @@ typedef struct lxc_attach_options_t {
 	{                                                                      \
 		/* .attach_flags = */   LXC_ATTACH_DEFAULT,                    \
 		/* .namespaces = */     -1,                                    \
-		/* .personality = */    -1,                                    \
+		/* .personality = */    0xffffffff,                            \
 		/* .initial_cwd = */    NULL,                                  \
 		/* .uid = */            (uid_t)-1,                             \
 		/* .gid = */            (gid_t)-1,                             \
diff --git a/src/lxc/confile.c b/src/lxc/confile.c
index b69ab3ad2d..409c547cb2 100644
--- a/src/lxc/confile.c
+++ b/src/lxc/confile.c
@@ -2825,7 +2825,7 @@ signed long lxc_config_parse_arch(const char *arch)
 			return pername[i].per;
 #endif
 
-	return -1;
+	return LXC_ARCH_UNCHANGED;
 }
 
 int lxc_fill_elevated_privileges(char *flaglist, int *flags)
diff --git a/src/lxc/confile.h b/src/lxc/confile.h
index 68d50fc804..f182dfaf45 100644
--- a/src/lxc/confile.h
+++ b/src/lxc/confile.h
@@ -78,7 +78,12 @@ __hidden extern bool lxc_config_define_load(struct lxc_list *defines, struct lxc
 
 __hidden extern void lxc_config_define_free(struct lxc_list *defines);
 
-/* needed for lxc-attach */
+#define LXC_ARCH_UNCHANGED 0xffffffffL
+/*
+ * Parse personality of the container. Returns LXC_ARCH_UNCHANGED if the
+ * personality is not know.
+ * (Used during attach.)
+ */
 __hidden extern signed long lxc_config_parse_arch(const char *arch);
 
 __hidden extern int lxc_fill_elevated_privileges(char *flaglist, int *flags);