From: Karel Zak <kzak@redhat.com>
Date: Tue, 28 Jan 2025 12:23:15 +0000 (+0100)
Subject: libmount: improve error messages in ID-mapping hook
X-Git-Tag: v2.42-start~64^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1760fd11641bc60d1a0f62583c9e5b63ddd7d8f2;p=thirdparty%2Futil-linux.git

libmount: improve error messages in ID-mapping hook

* save failed syscall status
* allow to read messages from kernel
* add proper error messages if kernel is silent

OLD:
  mount: /foo: mount failed: Unknown error 5013.
NEW:
  mount: /foo: mount_setattr() failed: cannot set ID-mapping: Operation not permitted.

Addresses: https://github.com/util-linux/util-linux/issues/3373
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/libmount/src/hook_idmap.c b/libmount/src/hook_idmap.c
index 4592f5ef6..e8c4cab5a 100644
--- a/libmount/src/hook_idmap.c
+++ b/libmount/src/hook_idmap.c
@@ -333,6 +333,7 @@ static int hook_mount_post(
 			    (recursive ? AT_RECURSIVE : 0));
 	if (fd_tree < 0) {
 		DBG(HOOK, ul_debugobj(hs, " failed to open tree"));
+		mnt_context_syscall_save_status(cxt, "open_tree", 0);
 		return -MNT_ERR_IDMAP;
 	}
 
@@ -341,7 +342,11 @@ static int hook_mount_post(
 			   AT_EMPTY_PATH | (recursive ? AT_RECURSIVE : 0),
 			   &attr, sizeof(attr));
 	if (rc < 0) {
-		DBG(HOOK, ul_debugobj(hs, " failed to set attributes"));
+		mnt_context_syscall_save_status(cxt, "mount_setattr", 0);
+		if (!mnt_context_read_mesgs(cxt, fd_tree)) {
+			/* TRANSLATORS: Don't translate "e ". It's a message classifier. */
+			mnt_context_sprintf_mesg(cxt, _("e cannot set ID-mapping: %m"));
+		}
 		goto done;
 	}
 
@@ -351,8 +356,13 @@ static int hook_mount_post(
 		umount2(target, MNT_DETACH);
 
 		rc = move_mount(fd_tree, "", -1, target, MOVE_MOUNT_F_EMPTY_PATH);
-		if (rc)
-			DBG(HOOK, ul_debugobj(hs, " failed to set move mount"));
+		if (rc < 0) {
+			mnt_context_syscall_save_status(cxt, "move_mount", 0);
+			if (!mnt_context_read_mesgs(cxt, fd_tree)) {
+				/* TRANSLATORS: Don't translate "e ". It's a message classifier. */
+				mnt_context_sprintf_mesg(cxt, _("e cannot set ID-mapping: %m"));
+			}
+		}
 	}
 done:
 	if (is_private)