db: allow read-only operations without cache

fixes #10748

4 files changed, 29 insertions, 11 deletions

diff --git a/src/apk_defines.h b/src/apk_defines.h
index e4f247a..fc975bd 100644
--- a/src/apk_defines.h
+++ b/src/apk_defines.h
@@ -37,6 +37,7 @@
 #define EAPKFORMAT		1026
 #define EAPKDEPFORMAT		1027
 #define EAPKDBFORMAT		1028
+#define EAPKCACHE		1029
 
 static inline void *ERR_PTR(long error) { return (void*) error; }
 static inline void *ERR_CAST(const void *ptr) { return (void*) ptr; }
diff --git a/src/database.c b/src/database.c
index 80f393d..f4169ff 100644
--- a/src/database.c
+++ b/src/database.c
@@ -1670,7 +1670,10 @@ int apk_db_open(struct apk_database *db, struct apk_db_options *dbopts)
 			mkdirat(db->root_fd, "var/cache", 0755);
 			mkdirat(db->root_fd, "var/cache/apk", 0755);
 			db->cache_fd = openat(db->root_fd, db->cache_dir, O_RDONLY | O_CLOEXEC);
-			if (db->cache_fd < 0) goto ret_errno;
+			if (db->cache_fd < 0) {
+				if (dbopts->open_flags & APK_OPENF_WRITE) goto ret_errno;
+				db->cache_fd = -EAPKCACHE;
+			}
 		}
 	}
 
@@ -1854,16 +1857,11 @@ void apk_db_close(struct apk_database *db)
 		db->cache_remount_dir = NULL;
 	}
 
-	if (db->keys_fd)
-		close(db->keys_fd);
-	if (db->cache_fd)
-		close(db->cache_fd);
-	if (db->root_fd)
-		close(db->root_fd);
-	if (db->lock_fd)
-		close(db->lock_fd);
-	if (db->root != NULL)
-		free(db->root);
+	if (db->keys_fd > 0) close(db->keys_fd);
+	if (db->cache_fd > 0) close(db->cache_fd);
+	if (db->root_fd > 0) close(db->root_fd);
+	if (db->lock_fd > 0) close(db->lock_fd);
+	free(db->root);
 }
 
 int apk_db_get_tag_id(struct apk_database *db, apk_blob_t tag)
diff --git a/src/io.c b/src/io.c
index b693ac4..22ef386 100644
--- a/src/io.c
+++ b/src/io.c
@@ -34,6 +34,11 @@
 
 size_t apk_io_bufsize = 128*1024;
 
+static inline int atfd_error(int atfd)
+{
+	return atfd < -1 && atfd != AT_FDCWD;
+}
+
 static void apk_file_meta_from_fd(int fd, struct apk_file_meta *meta)
 {
 	struct stat st;
@@ -314,6 +319,7 @@ struct apk_istream *apk_istream_tee(struct apk_istream *from, int atfd, const ch
 	int fd, r;
 
 	if (IS_ERR_OR_NULL(from)) return ERR_CAST(from);
+	if (atfd_error(atfd)) return ERR_PTR(atfd);
 
 	fd = openat(atfd, to, O_CREAT | O_RDWR | O_TRUNC | O_CLOEXEC,
 		    S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
@@ -482,6 +488,8 @@ struct apk_istream *apk_istream_from_file(int atfd, const char *file)
 {
 	int fd;
 
+	if (atfd_error(atfd)) return ERR_PTR(atfd);
+
 	fd = openat(atfd, file, O_RDONLY | O_CLOEXEC);
 	if (fd < 0) return ERR_PTR(-errno);
 
@@ -604,6 +612,8 @@ apk_blob_t apk_blob_from_file(int atfd, const char *file)
 	struct stat st;
 	char *buf;
 
+	if (atfd_error(atfd)) return APK_BLOB_NULL;
+
 	fd = openat(atfd, file, O_RDONLY | O_CLOEXEC);
 	if (fd < 0)
 		return APK_BLOB_NULL;
@@ -631,6 +641,8 @@ int apk_blob_to_file(int atfd, const char *file, apk_blob_t b, unsigned int flag
 {
 	int fd, r, len;
 
+	if (atfd_error(atfd)) return atfd;
+
 	fd = openat(atfd, file, O_CREAT | O_WRONLY | O_CLOEXEC, 0644);
 	if (fd < 0)
 		return -errno;
@@ -707,6 +719,9 @@ int apk_fileinfo_get(int atfd, const char *filename, unsigned int flags,
 	unsigned int xattr_checksum = (flags >> 8) & 0xff;
 	int atflags = 0;
 
+	if (atfd_error(atfd)) return atfd;
+
+	memset(fi, 0, sizeof *fi);
 	if (flags & APK_FI_NOFOLLOW)
 		atflags |= AT_SYMLINK_NOFOLLOW;
 
@@ -959,6 +974,8 @@ struct apk_ostream *apk_ostream_to_file(int atfd,
 	struct apk_ostream *os;
 	int fd;
 
+	if (atfd_error(atfd)) return ERR_PTR(atfd);
+
 	fd = openat(atfd, tmpfile ?: file, O_CREAT | O_RDWR | O_TRUNC | O_CLOEXEC, mode);
 	if (fd < 0) return ERR_PTR(-errno);
 
diff --git a/src/print.c b/src/print.c
index 81a4faf..5be5460 100644
--- a/src/print.c
+++ b/src/print.c
@@ -185,6 +185,8 @@ const char *apk_error_str(int error)
 		return "package dependency format error";
 	case EAPKDBFORMAT:
 		return "database file format error";
+	case EAPKCACHE:
+		return "cache not available";
 	default:
 		return strerror(error);
 	}