check: verify ino and dev of overlayfs files in /proc/pid/maps

Check that the file device and inode shown in /proc/pid/maps match
values returned by stat(2).

Signed-off-by: Andrei Vagin <[email protected]>

criu/cr-check.c

@@ -53,6 +53,8 @@
 #include "restorer.h"
 #include "uffd.h"
 #include "linux/aio_abi.h"
+#include "syscall.h"
+#include "mount-v2.h"
 
 #include "images/inventory.pb-c.h"
 
@@ -721,7 +723,7 @@ static int check_special_mapping_mremap(void)
 			return -1;
 		}
 		/* Probably, we're interrupted with a signal - cleanup */
-		pr_err("Failed to wait for a child %d\n", errno);
+		pr_perror("Failed to wait for a child");
 		kill(child, SIGKILL);
 		waitpid(child, NULL, 0);
 		return -1;
@@ -1382,6 +1384,184 @@ static int check_ipv6_freebind(void)
 	return 0;
 }
 
+static long get_file_dev_and_inode(void *addr, struct statx *stx)
+{
+	char buf[4096];
+	FILE *mapf;
+
+	mapf = fopen("/proc/self/maps", "r");
+	if (mapf == NULL) {
+		pr_perror("fopen(/proc/self/maps)");
+		return -1;
+	}
+
+	while (fgets(buf, sizeof(buf), mapf)) {
+		unsigned long start, end;
+		uint32_t maj, min;
+		__u64 ino;
+
+		if (sscanf(buf, "%lx-%lx %*s %*s %x:%x %llu",
+				&start, &end, &maj, &min, &ino) != 5) {
+			pr_perror("unable to parse: %s", buf);
+			return -1;
+		}
+		if (start == (unsigned long)addr) {
+			stx->stx_dev_major = maj;
+			stx->stx_dev_minor = min;
+			stx->stx_ino = ino;
+			return 0;
+		}
+	}
+
+	pr_err("unable to find the mapping\n");
+	return -1;
+}
+
+static int ovl_mount(void)
+{
+	int tmpfs, fsfd, ovl;
+
+	fsfd = sys_fsopen("tmpfs", 0);
+	if (fsfd == -1) {
+		pr_perror("Unable to fsopen tmpfs");
+		return -1;
+	}
+
+	if (sys_fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0) == -1) {
+		pr_perror("Unable to create tmpfs mount");
+		return -1;
+	}
+
+	tmpfs = sys_fsmount(fsfd, 0, 0);
+	if (tmpfs == -1) {
+		pr_perror("Unable to mount tmpfs");
+		return -1;
+	}
+
+	close(fsfd);
+
+	/* overlayfs can't be constructed on top of a detached mount. */
+	if (sys_move_mount(tmpfs, "", AT_FDCWD, "/tmp", MOVE_MOUNT_F_EMPTY_PATH)) {
+		pr_perror("Unable to attach tmpfs mount");
+		return -1;
+	}
+	close(tmpfs);
+
+	if (chdir("/tmp")) {
+		pr_perror("Unable to change working directory");
+		return -1;
+	}
+
+	if (mkdir("/tmp/w", 0755) == -1 ||
+	    mkdir("/tmp/u", 0755) == -1 ||
+	    mkdir("/tmp/l", 0755) == -1) {
+		pr_perror("mkdir");
+		return -1;
+	}
+
+	fsfd = sys_fsopen("overlay", 0);
+	if (fsfd == -1) {
+		pr_perror("Unable to fsopen overlayfs");
+		return -1;
+	}
+	if (sys_fsconfig(fsfd, FSCONFIG_SET_STRING, "source", "test", 0) == -1 ||
+	    sys_fsconfig(fsfd, FSCONFIG_SET_STRING, "lowerdir", "/tmp/l", 0) == -1 ||
+	    sys_fsconfig(fsfd, FSCONFIG_SET_STRING, "upperdir", "/tmp/u", 0) == -1 ||
+	    sys_fsconfig(fsfd, FSCONFIG_SET_STRING, "workdir", "/tmp/w", 0) == -1) {
+		pr_perror("Unable to configure overlayfs");
+		return -1;
+	}
+	if (sys_fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0) == -1) {
+		pr_perror("Unable to create overlayfs");
+		return -1;
+	}
+	ovl = sys_fsmount(fsfd, 0, 0);
+	if (ovl == -1) {
+		pr_perror("Unable to mount overlayfs");
+		return -1;
+	}
+
+	return ovl;
+}
+
+/*
+ * Check that the file device and inode shown in /proc/pid/maps match values
+ * returned by stat(2).
+ */
+static int do_check_overlayfs_maps(void)
+{
+	struct statx stx, mstx;
+	int ovl, fd;
+	void *addr;
+
+	/* Create a new mount namespace to not care about cleaning test mounts. */
+	if (unshare(CLONE_NEWNS) == -1) {
+		pr_warn("Unable to create a new mount namespace\n");
+		return 0;
+	}
+
+	if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) == -1) {
+		pr_perror("Unable to remount / with MS_SLAVE");
+		return -1;
+	}
+
+	ovl = ovl_mount();
+	if (ovl == -1)
+		return -1;
+
+	fd = openat(ovl, "test", O_RDWR | O_CREAT, 0644);
+	if (fd == -1) {
+		pr_perror("Unable to open a test file");
+		return -1;
+	}
+
+	addr = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_FILE | MAP_SHARED, fd, 0);
+	if (addr == MAP_FAILED) {
+		pr_perror("Unable to map the test file");
+		return -1;
+	}
+
+	if (get_file_dev_and_inode(addr, &mstx))
+		return -1;
+	if (statx(fd, "", AT_EMPTY_PATH | AT_STATX_SYNC_AS_STAT, STATX_INO, &stx)) {
+		pr_perror("statx");
+		return -1;
+	}
+
+	if (stx.stx_dev_major != mstx.stx_dev_major ||
+	    stx.stx_dev_minor != mstx.stx_dev_minor ||
+	    stx.stx_ino != mstx.stx_ino) {
+		pr_err("unmatched dev:ino %x:%x:%llx (expected %x:%x:%llx)\n",
+			mstx.stx_dev_major, mstx.stx_dev_minor, mstx.stx_ino,
+			stx.stx_dev_major, stx.stx_dev_minor, stx.stx_ino);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int check_overlayfs_maps(void)
+{
+	pid_t pid;
+	int status;
+
+	pid = fork();
+	if (pid == -1) {
+		pr_perror("Unable to fork a child");
+		return -1;
+	}
+	if (pid == 0) {
+		if (do_check_overlayfs_maps())
+			exit(1);
+		exit(0);
+	}
+	if (waitpid(pid, &status, 0) == -1) {
+		pr_perror("waitpid");
+		return -1;
+	}
+	return status == 0 ? 0 : -1;
+}
+
 static int (*chk_feature)(void);
 
 /*
@@ -1502,6 +1682,7 @@ int cr_check(void)
 		ret |= check_openat2();
 		ret |= check_ptrace_get_rseq_conf();
 		ret |= check_ipv6_freebind();
+		ret |= check_overlayfs_maps();
 
 		if (kdat.lsm == LSMTYPE__APPARMOR)
 			ret |= check_apparmor_stacking();
@@ -1623,6 +1804,7 @@ static struct feature_list feature_list[] = {
 	{ "openat2", check_openat2 },
 	{ "get_rseq_conf", check_ptrace_get_rseq_conf },
 	{ "ipv6_freebind", check_ipv6_freebind },
+	{ "overlayfs_maps", check_overlayfs_maps },
 	{ NULL, NULL },
 };
 

scripts/ci/run-ci-tests.sh

@@ -293,7 +293,14 @@ ip net add test
 # This is a temporary workaround until fixed in the kernel.
 # The kernel currently does not show correct device and inode numbers in /proc/pid/maps
 # for stackable file systems.
-if capsh --supports=cap_checkpoint_restore && unshare -c /bin/true && [ ! -e /run/.containerenv ]; then
+skip=0
+findmnt -no FSTYPE / | grep overlay && {
+	./criu/criu check --feature overlayfs_maps || skip=1
+}
+unshare -c /bin/true || skip=1
+capsh --supports=cap_checkpoint_restore || skip=1
+
+if [ "$skip" == 0 ]; then
 	make -C test/zdtm/ cleanout
 	rm -rf test/dump
 	setcap cap_checkpoint_restore,cap_sys_ptrace+eip criu/criu