Improve builtin selinux implementation

native/jni/utils/file.cpp

@@ -27,15 +27,17 @@ static int is_excl(const char *name) {
 	return 0;
 }
 
-int fd_getpath(int fd, char *path, size_t size) {
+ssize_t fd_path(int fd, char *path, size_t size) {
 	snprintf(path, size, "/proc/self/fd/%d", fd);
-	return xreadlink(path, path, size) == -1;
+	return xreadlink(path, path, size);
 }
 
-int fd_getpathat(int dirfd, const char *name, char *path, size_t size) {
+int fd_pathat(int dirfd, const char *name, char *path, size_t size) {
-	if (fd_getpath(dirfd, path, size))
+	ssize_t len = fd_path(dirfd, path, size);
-		return 1;
+	if (len < 0)
-	snprintf(path, size, "%s/%s", path, name);
+		return -1;
+	path[len] = '/';
+	strlcpy(&path[len + 1], name, size - len - 1);
 	return 0;
 }
 
@@ -85,7 +87,7 @@ void rm_rf(const char *path) {
 	if (lstat(path, &st) < 0)
 		return;
 	if (S_ISDIR(st.st_mode)) {
-		int fd = open(path, O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
+		int fd = open(path, O_RDONLY | O_CLOEXEC);
 		frm_rf(fd);
 		close(fd);
 	}
@@ -211,7 +213,7 @@ void clone_dir(int src, int dest) {
 		case DT_REG:
 			destfd = xopenat(dest, entry->d_name, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC);
 			srcfd = xopenat(src, entry->d_name, O_RDONLY | O_CLOEXEC);
-			xsendfile(destfd, srcfd, 0, a.st.st_size);
+			xsendfile(destfd, srcfd, nullptr, a.st.st_size);
 			fsetattr(destfd, &a);
 			close(destfd);
 			close(srcfd);
@@ -263,16 +265,21 @@ int getattr(const char *path, struct file_attr *a) {
 	return 0;
 }
 
-int getattrat(int dirfd, const char *pathname, struct file_attr *a) {
+int getattrat(int dirfd, const char *name, struct file_attr *a) {
-	char path[PATH_MAX];
+	char path[4096];
-	fd_getpathat(dirfd, pathname, path, sizeof(path));
+	fd_pathat(dirfd, name, path, sizeof(path));
 	return getattr(path, a);
 }
 
 int fgetattr(int fd, struct file_attr *a) {
-	char path[PATH_MAX];
+	if (xfstat(fd, &a->st) < 0)
-	fd_getpath(fd, path, sizeof(path));
+		return -1;
-	return getattr(path, a);
+	char *con;
+	if (fgetfilecon(fd, &con) < 0)
+		return -1;
+	strcpy(a->con, con);
+	freecon(con);
+	return 0;
 }
 
 int setattr(const char *path, struct file_attr *a) {
@@ -280,21 +287,25 @@ int setattr(const char *path, struct file_attr *a) {
 		return -1;
 	if (chown(path, a->st.st_uid, a->st.st_gid) < 0)
 		return -1;
-	if (strlen(a->con) && lsetfilecon(path, a->con) < 0)
+	if (a->con[0] && lsetfilecon(path, a->con) < 0)
 		return -1;
 	return 0;
 }
 
-int setattrat(int dirfd, const char *pathname, struct file_attr *a) {
+int setattrat(int dirfd, const char *name, struct file_attr *a) {
-	char path[PATH_MAX];
+	char path[4096];
-	fd_getpathat(dirfd, pathname, path, sizeof(path));
+	fd_pathat(dirfd, name, path, sizeof(path));
 	return setattr(path, a);
 }
 
 int fsetattr(int fd, struct file_attr *a) {
-	char path[PATH_MAX];
+	if (fchmod(fd, a->st.st_mode & 0777) < 0)
-	fd_getpath(fd, path, sizeof(path));
+		return -1;
-	return setattr(path, a);
+	if (fchown(fd, a->st.st_uid, a->st.st_gid) < 0)
+		return -1;
+	if (a->con[0] && fsetfilecon(fd, a->con) < 0)
+		return -1;
+	return 0;
 }
 
 void clone_attr(const char *source, const char *target) {
@@ -346,17 +357,6 @@ void full_read(const char *filename, void **buf, size_t *size) {
 	close(fd);
 }
 
-void full_read_at(int dirfd, const char *filename, void **buf, size_t *size) {
-	int fd = xopenat(dirfd, filename, O_RDONLY | O_CLOEXEC);
-	if (fd < 0) {
-		*buf = nullptr;
-		*size = 0;
-		return;
-	}
-	fd_full_read(fd, buf, size);
-	close(fd);
-}
-
 void write_zero(int fd, size_t size) {
 	char buf[4096] = {0};
 	size_t len;

native/jni/utils/include/selinux.h

@@ -8,8 +8,12 @@ extern void (*freecon)(char * con);
 extern int (*setcon)(const char *con);
 extern int (*getfilecon)(const char *path, char **con);
 extern int (*lgetfilecon)(const char *path, char **con);
+extern int (*fgetfilecon)(int fd, char **con);
 extern int (*setfilecon)(const char *path, const char *con);
 extern int (*lsetfilecon)(const char *path, const char *con);
+extern int (*fsetfilecon)(int fd, const char *con);
+void getfilecon_at(int dirfd, const char *name, char **con);
+void setfilecon_at(int dirfd, const char *name, const char *con);
 
 void selinux_builtin_impl();
 void dload_selinux();

native/jni/utils/include/utils.h

@@ -51,6 +51,7 @@ int xpthread_create(pthread_t *thread, const pthread_attr_t *attr,
 	void *(*start_routine) (void *), void *arg);
 int xstat(const char *pathname, struct stat *buf);
 int xlstat(const char *pathname, struct stat *buf);
+int xfstat(int fd, struct stat *buf);
 int xdup2(int oldfd, int newfd);
 int xdup3(int oldfd, int newfd, int flags);
 ssize_t xreadlink(const char *pathname, char *buf, size_t bufsiz);
@@ -103,8 +104,8 @@ struct file_attr {
 	char con[128];
 };
 
-int fd_getpath(int fd, char *path, size_t size);
+ssize_t fd_path(int fd, char *path, size_t size);
-int fd_getpathat(int dirfd, const char *name, char *path, size_t size);
+int fd_pathat(int dirfd, const char *name, char *path, size_t size);
 int mkdirs(const char *pathname, mode_t mode);
 void post_order_walk(int dirfd, void (*fn)(int, struct dirent *));
 void rm_rf(const char *path);
@@ -115,17 +116,16 @@ void cp_afc(const char *source, const char *destination);
 void link_dir(int src, int dest);
 void clone_dir(int src, int dest);
 int getattr(const char *path, struct file_attr *a);
-int getattrat(int dirfd, const char *pathname, struct file_attr *a);
+int getattrat(int dirfd, const char *name, struct file_attr *a);
 int fgetattr(int fd, struct file_attr *a);
 int setattr(const char *path, struct file_attr *a);
-int setattrat(int dirfd, const char *pathname, struct file_attr *a);
+int setattrat(int dirfd, const char *name, struct file_attr *a);
 int fsetattr(int fd, struct file_attr *a);
 void fclone_attr(int sourcefd, int targetfd);
 void clone_attr(const char *source, const char *target);
 void mmap_ro(const char *filename, void **buf, size_t *size);
 void fd_full_read(int fd, void **buf, size_t *size);
 void full_read(const char *filename, void **buf, size_t *size);
-void full_read_at(int dirfd, const char *filename, void **buf, size_t *size);
 void write_zero(int fd, size_t size);
 
 #ifdef __cplusplus

native/jni/utils/selinux.cpp

@@ -25,6 +25,13 @@ static int stub(const char *, char **ctx) {
 	return 0;
 }
 
+static int stub(int, const char *) { return 0; }
+
+static int stub(int, char **ctx) {
+	*ctx = strdup("");
+	return 0;
+}
+
 // Builtin implementation
 
 static void __freecon(char *s) {
@@ -44,7 +51,10 @@ static int __setcon(const char *ctx) {
 static int __getfilecon(const char *path, char **ctx) {
 	char buf[1024];
 	int rc = syscall(__NR_getxattr, path, XATTR_NAME_SELINUX, buf, sizeof(buf) - 1);
-	if (rc > 0)
+	if (rc < 0) {
+		errno = -rc;
+		return -1;
+	}
 	*ctx = strdup(buf);
 	return rc;
 }
@@ -52,17 +62,50 @@ static int __getfilecon(const char *path, char **ctx) {
 static int __lgetfilecon(const char *path, char **ctx) {
 	char buf[1024];
 	int rc = syscall(__NR_lgetxattr, path, XATTR_NAME_SELINUX, buf, sizeof(buf) - 1);
-	if (rc > 0)
+	if (rc < 0) {
+		errno = -rc;
+		return -1;
+	}
+	*ctx = strdup(buf);
+	return rc;
+}
+
+static int __fgetfilecon(int fd, char **ctx) {
+	char buf[1024];
+	int rc = syscall(__NR_fgetxattr, fd, XATTR_NAME_SELINUX, buf, sizeof(buf) - 1);
+	if (rc < 0) {
+		errno = -rc;
+		return -1;
+	}
 	*ctx = strdup(buf);
 	return rc;
 }
 
 static int __setfilecon(const char *path, const char *ctx) {
-	return syscall(__NR_setxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
+	int rc = syscall(__NR_setxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
+	if (rc) {
+		errno = -rc;
+		return -1;
+	}
+	return 0;
 }
 
 static int __lsetfilecon(const char *path, const char *ctx) {
-	return syscall(__NR_lsetxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
+	int rc = syscall(__NR_lsetxattr, path, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
+	if (rc) {
+		errno = -rc;
+		return -1;
+	}
+	return 0;
+}
+
+static int __fsetfilecon(int fd, const char *ctx) {
+	int rc = syscall(__NR_fsetxattr, fd, XATTR_NAME_SELINUX, ctx, strlen(ctx) + 1, 0);
+	if (rc) {
+		errno = -rc;
+		return -1;
+	}
+	return 0;
 }
 
 // Function pointers
@@ -71,15 +114,32 @@ void (*freecon)(char *) = __freecon;
 int (*setcon)(const char *) = stub;
 int (*getfilecon)(const char *, char **) = stub;
 int (*lgetfilecon)(const char *, char **) = stub;
+int (*fgetfilecon)(int, char **) = stub;
 int (*setfilecon)(const char *, const char *) = stub;
 int (*lsetfilecon)(const char *, const char *) = stub;
+int (*fsetfilecon)(int, const char *) = stub;
+
+void getfilecon_at(int dirfd, const char *name, char **con) {
+	char path[4096];
+	fd_pathat(dirfd, name, path, sizeof(path));
+	if (lgetfilecon(path, con))
+		*con = strdup("");
+}
+
+void setfilecon_at(int dirfd, const char *name, const char *con) {
+	char path[4096];
+	fd_pathat(dirfd, name, path, sizeof(path));
+	lsetfilecon(path, con);
+}
 
 void selinux_builtin_impl() {
 	setcon = __setcon;
 	getfilecon = __getfilecon;
 	lgetfilecon = __lgetfilecon;
+	fgetfilecon = __fgetfilecon;
 	setfilecon = __setfilecon;
 	lsetfilecon = __lsetfilecon;
+	fsetfilecon = __fsetfilecon;
 }
 
 void dload_selinux() {
@@ -95,33 +155,32 @@ void dload_selinux() {
 static void restore_syscon(int dirfd) {
 	struct dirent *entry;
 	DIR *dir;
+	char *con;
 
-	char path[PATH_MAX], *con;
+	fgetfilecon(dirfd, &con);
-
-	fd_getpath(dirfd, path, sizeof(path));
-	size_t len = strlen(path);
-	getfilecon(path, &con);
 	if (strlen(con) == 0 || strcmp(con, UNLABEL_CON) == 0)
-		lsetfilecon(path, SYSTEM_CON);
+		fsetfilecon(dirfd, SYSTEM_CON);
 	freecon(con);
 
 	dir = xfdopendir(dirfd);
 	while ((entry = xreaddir(dir))) {
 		if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
 			continue;
+		int fd = openat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
 		if (entry->d_type == DT_DIR) {
-			int fd = xopenat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
 			restore_syscon(fd);
-			close(fd);
+		} else if (entry->d_type == DT_REG) {
-		} else {
+			fgetfilecon(fd, &con);
-			path[len] = '/';
+			if (con[0] == '\0' || strcmp(con, UNLABEL_CON) == 0)
-			strcpy(path + len + 1, entry->d_name);
+				fsetfilecon(fd, SYSTEM_CON);
-			lgetfilecon(path, &con);
+			freecon(con);
-			if (strlen(con) == 0 || strcmp(con, UNLABEL_CON) == 0)
+		} else if (entry->d_type == DT_LNK) {
-				lsetfilecon(path, SYSTEM_CON);
+			getfilecon_at(dirfd, entry->d_name, &con);
+			if (con[0] == '\0' || strcmp(con, UNLABEL_CON) == 0)
+				setfilecon_at(dirfd, entry->d_name, con);
 			freecon(con);
-			path[len] = '\0';
 		}
+		close(fd);
 	}
 }
 
@@ -129,28 +188,21 @@ static void restore_magiskcon(int dirfd) {
 	struct dirent *entry;
 	DIR *dir;
 
-	char path[PATH_MAX];
+	fsetfilecon(dirfd, MAGISK_CON);
-
+	fchown(dirfd, 0, 0);
-	fd_getpath(dirfd, path, sizeof(path));
-	size_t len = strlen(path);
-	lsetfilecon(path, MAGISK_CON);
-	lchown(path, 0, 0);
 
 	dir = xfdopendir(dirfd);
 	while ((entry = xreaddir(dir))) {
 		if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
 			continue;
-		if (entry->d_type == DT_DIR) {
 		int fd = xopenat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC);
+		if (entry->d_type == DT_DIR) {
 			restore_magiskcon(fd);
-			close(fd);
+		} else if (entry->d_type) {
-		} else {
+			fsetfilecon(fd, MAGISK_CON);
-			path[len] = '/';
+			fchown(fd, 0, 0);
-			strcpy(path + len + 1, entry->d_name);
-			lsetfilecon(path, MAGISK_CON);
-			lchown(path, 0, 0);
-			path[len] = '\0';
 		}
+		close(fd);
 	}
 }
 

native/jni/utils/xwrap.cpp

@@ -262,6 +262,14 @@ int xlstat(const char *pathname, struct stat *buf) {
 	return ret;
 }
 
+int xfstat(int fd, struct stat *buf) {
+	int ret = fstat(fd, buf);
+	if (ret == -1) {
+		PLOGE("fstat %d", fd);
+	}
+	return ret;
+}
+
 int xdup2(int oldfd, int newfd) {
 	int ret = dup2(oldfd, newfd);
 	if (ret == -1) {