xattr-util: merge various getxattr()/listxattr() helpers into getxattr_at_malloc() + listxattr_at_malloc()

Unfortunately fgetxattr() and flistxattr() don't work via O_PATH fds.
Let's thus add fallbacks to go via /proc/self/fd/ in these cases.

Also, let's merge all the various flavours we have here into singular
implementations that can do everything we need:

1. malloc() loop handling
2. by fd, by path, or combination (i.e. a proper openat() like API)
3. work on O_PATH

src/shared/cgroup-show.c

@@ -127,7 +127,7 @@ static int show_cgroup_name(
         bool delegate = false;
         int r;
 
-        r = getxattr_malloc(path, "trusted.delegate", &b, false);
+        r = lgetxattr_malloc(path, "trusted.delegate", &b);
         if (r < 0) {
                 if (r != -ENODATA)
                         log_debug_errno(r, "Failed to read trusted.delegate extended attribute: %m");

src/shared/discover-image.c

@@ -334,7 +334,7 @@ static int image_make(
                 if (!ret)
                         return 0;
 
-                (void) fd_getcrtime_at(dfd, filename, &crtime, 0);
+                (void) fd_getcrtime_at(dfd, filename, AT_SYMLINK_FOLLOW, &crtime);
 
                 if (!pretty) {
                         r = extract_pretty(filename, ".raw", &pretty_buffer);

src/shared/dissect-image.c

@@ -2765,7 +2765,7 @@ int verity_settings_load(
                          * that doesn't exist for /usr */
 
                         if (designator < 0 || designator == PARTITION_ROOT) {
-                                r = getxattr_malloc(image, "user.verity.roothash", &text, true);
+                                r = getxattr_malloc(image, "user.verity.roothash", &text);
                                 if (r < 0) {
                                         _cleanup_free_ char *p = NULL;
 
@@ -2794,7 +2794,7 @@ int verity_settings_load(
                                  * `usrhash`, because `usrroothash` or `rootusrhash` would just be too
                                  * confusing. We thus drop the reference to the root of the Merkle tree, and
                                  * just indicate which file system it's about. */
-                                r = getxattr_malloc(image, "user.verity.usrhash", &text, true);
+                                r = getxattr_malloc(image, "user.verity.usrhash", &text);
                                 if (r < 0) {
                                         _cleanup_free_ char *p = NULL;
 

src/shared/smack-util.c

@@ -52,7 +52,7 @@ int mac_smack_read(const char *path, SmackAttr attr, char **label) {
         if (!mac_smack_use())
                 return 0;
 
-        return getxattr_malloc(path, smack_attr_to_string(attr), label, true);
+        return getxattr_malloc(path, smack_attr_to_string(attr), label);
 }
 
 int mac_smack_read_fd(int fd, SmackAttr attr, char **label) {
@@ -166,7 +166,7 @@ static int smack_fix_fd(int fd, const char *abspath, LabelFixFlags flags) {
                         return 0;
 
                 /* If the old label is identical to the new one, suppress any kind of error */
-                if (getxattr_malloc(FORMAT_PROC_FD_PATH(fd), "security.SMACK64", &old_label, false) >= 0 &&
+                if (lgetxattr_malloc(FORMAT_PROC_FD_PATH(fd), "security.SMACK64", &old_label) >= 0 &&
                     streq(old_label, label))
                         return 0;