From: Michael Tremer <michael.tremer@ipfire.org>
Date: Sun, 17 Jul 2022 18:09:29 +0000 (+0000)
Subject: execute: Switch back to chroot()
X-Git-Tag: 0.9.28~695
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c7b9ea4f1febdb8f56dfe775c5c2d26963d72ecc;p=pakfire.git

execute: Switch back to chroot()

pivot_root() seems to be very complicated to use and will require us to
have the container run on a different file system. That is however not
possible when Pakfire is running as an un-privileged user.

Since pivot_root() does not seem to offer any advantages over chroot(),
we switch back to chroot() which is easier to use.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---

diff --git a/src/libpakfire/execute.c b/src/libpakfire/execute.c
index f4cde9465..1780b3436 100644
--- a/src/libpakfire/execute.c
+++ b/src/libpakfire/execute.c
@@ -84,10 +84,6 @@ static int clone3(struct clone_args* args, size_t size) {
 	return syscall(__NR_clone3, args, size);
 }
 
-static int pivot_root(const char* new_root, const char* put_old) {
-	return syscall(__NR_pivot_root, new_root, put_old);
-}
-
 static int pakfire_execute_buffer_is_full(const struct pakfire_execute_buffer* buffer) {
 	return (sizeof(buffer->data) == buffer->used);
 }
@@ -547,8 +543,6 @@ static int pakfire_execute_fork(void* data) {
 	const char* root = pakfire_get_path(pakfire);
 	const char* arch = pakfire_get_arch(pakfire);
 
-	char oldroot[PATH_MAX];
-
 	DEBUG(pakfire, "Execution environment has been forked as PID %d\n", getpid());
 	DEBUG(pakfire, "	root	: %s\n", root);
 	DEBUG(pakfire, "	cgroup  : %s\n", env->cgroup);
@@ -561,11 +555,6 @@ static int pakfire_execute_fork(void* data) {
 
 	// Change root (unless root is /)
 	if (strcmp(root, "/") != 0) {
-		// Disable mount propagation on /
-		r = pakfire_disable_mount_propagation(pakfire, "/");
-		if (r)
-			return r;
-
 		// Mount everything
 		r = pakfire_mount_all(pakfire, MOUNT_IN_NEW_NS);
 		if (r)
@@ -574,23 +563,10 @@ static int pakfire_execute_fork(void* data) {
 		// Log all mountpoints
 		pakfire_mount_list(pakfire);
 
-		// Move the old root to here
-		r = pakfire_string_format(oldroot, "%s/.oldroot.XXXXXX", root);
-		if (r < 0) {
-			ERROR(pakfire, "Could not figure out where the old root directory is going: %m\n");
-			return r;
-		}
-
-		// Create temporary directory
-		if (!pakfire_mkdtemp(oldroot)) {
-			ERROR(pakfire, "Could not create temporary directory: %m\n");
-			return r;
-		}
-
-		// Call pivot_root()
-		r = pivot_root(root, oldroot);
+		// Call chroot()
+		r = chroot(root);
 		if (r) {
-			ERROR(pakfire, "pivot_root() to %s failed: %m\n", root);
+			ERROR(pakfire, "chroot() to %s failed: %m\n", root);
 			return 1;
 		}
 
@@ -600,22 +576,6 @@ static int pakfire_execute_fork(void* data) {
 			ERROR(pakfire, "chdir() after chroot() failed: %m\n");
 			return 1;
 		}
-
-		const char* __oldroot = oldroot + strlen(root);
-
-		// Umount the old root directory
-		r = umount2(__oldroot, MNT_DETACH);
-		if (r) {
-			ERROR(pakfire, "Could not umount old root directory: %m\n");
-			return r;
-		}
-
-		// Remove the old root directory
-		r = rmdir(__oldroot);
-		if (r) {
-			ERROR(pakfire, "Could not remove the old root directory: %m\n");
-			return r;
-		}
 	}
 
 	// Set personality
diff --git a/src/libpakfire/include/pakfire/mount.h b/src/libpakfire/include/pakfire/mount.h
index 6f1b9a056..fba1ae735 100644
--- a/src/libpakfire/include/pakfire/mount.h
+++ b/src/libpakfire/include/pakfire/mount.h
@@ -30,8 +30,6 @@ enum pakfire_mount_flags {
 	MOUNT_IN_NEW_NS = (1 << 0),
 };
 
-int pakfire_disable_mount_propagation(struct pakfire* pakfire, const char* path);
-
 int pakfire_mount_list(struct pakfire* pakfire);
 
 int pakfire_mount(struct pakfire* pakfire, const char* source, const char* target,