[PATCH v3] ntfs: mount hibernated volumes read-only regardless of errors=

[Hongling Zeng]

The hibernation check in load_system_files() only converts the
superblock to read-only under errors=remount-ro.  With the default
errors=continue (and with errors=panic), a hibernated volume is
mounted read-write and the mount-time $LogFile emptying writes to it,
although a hibernated volume must not be written to at all.

Drop the on_errors term so that a hibernated volume, or a volume whose
hibernation state cannot be determined, always mounts read-only.
NVolErrors() is still recorded, so ntfs_reconfigure() keeps refusing
remounts to read-write, and the $LogFile emptying is skipped by its
!sb_rdonly() check.

Also change the ntfs_error() calls inside
check_windows_hibernation_status() to ntfs_warning(): they run before
SB_RDONLY is set, so errors=panic could panic there, while the warnings
preserve diagnostics for already read-only mounts.  The read-only
fallback message is logged unconditionally: with SB_RDONLY set, or on
an already read-only mount, ntfs_error() cannot panic, and the reason
for NVolErrors() stays visible.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hongling Zeng <zenghongling@xxxxxxxxxx>

---
Changes in v3:
 -Use ntfs_warning() for the hibernation diagnostics so that
  errors=panic cannot fire on this path.
 -Always log the read-only fallback message, including on already
  read-only mounts.
---
 fs/ntfs/super.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/fs/ntfs/super.c b/fs/ntfs/super.c
index f4a73e45773d..d1edf1a891e8 100644
--- a/fs/ntfs/super.c
+++ b/fs/ntfs/super.c
@@ -1169,7 +1169,7 @@ static int check_windows_hibernation_status(struct ntfs_volume *vol)
 			return 0;
 		}
 		/* A real error occurred. */
-		ntfs_error(vol->sb, "Failed to find inode number for hiberfil.sys.");
+		ntfs_warning(vol->sb, "Failed to find inode number for hiberfil.sys.");
 		return ret;
 	}
 	/* Get the inode. */
@@ -1177,7 +1177,7 @@ static int check_windows_hibernation_status(struct ntfs_volume *vol)
 	if (IS_ERR(vi)) {
 		if (!IS_ERR(vi))
 			iput(vi);
-		ntfs_error(vol->sb, "Failed to load hiberfil.sys.");
+		ntfs_warning(vol->sb, "Failed to load hiberfil.sys.");
 		return IS_ERR(vi) ? PTR_ERR(vi) : -EIO;
 	}
 	if (unlikely(i_size_read(vi) < NTFS_HIBERFIL_HEADER_SIZE)) {
@@ -1188,7 +1188,7 @@ static int check_windows_hibernation_status(struct ntfs_volume *vol)
 
 	folio = read_mapping_folio(vi->i_mapping, 0, NULL);
 	if (IS_ERR(folio)) {
-		ntfs_error(vol->sb, "Failed to read from hiberfil.sys.");
+		ntfs_warning(vol->sb, "Failed to read from hiberfil.sys.");
 		ret = PTR_ERR(folio);
 		goto iput_out;
 	}
@@ -1581,11 +1581,16 @@ static bool load_system_files(struct ntfs_volume *vol)
 		const char *es1;
 
 		es1 = err < 0 ? es1a : es1b;
-		/* If a read-write mount, convert it to a read-only mount. */
-		if (!sb_rdonly(sb) && vol->on_errors == ON_ERRORS_REMOUNT_RO) {
+		/*
+		 * A Windows hibernation image is not a filesystem error, so
+		 * this is a safety interlock rather than something the
+		 * errors= policy may downgrade: always convert a read-write
+		 * mount to read-only.
+		 */
+		if (!sb_rdonly(sb))
 			sb->s_flags |= SB_RDONLY;
-			ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
-		}
+
+		ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
 		NVolSetErrors(vol);
 	}
 
-- 
2.25.1