NTFS: Detect the case when Windows has been suspended to disk on the volume

      to be mounted and if this is the case do not allow (re)mounting
      read-write.  This is done by parsing hiberfil.sys if present.
Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

fs/ntfs/ChangeLog

@@ -125,6 +125,9 @@ ToDo/Notes:
 	  if the runlist was not mapped at all and a mapping error occured we
 	  would leave the runlist locked on exit to the function so that the
 	  next access to the same file would try to take the lock and deadlock.
+	- Detect the case when Windows has been suspended to disk on the volume
+	  to be mounted and if this is the case do not allow (re)mounting
+	  read-write.  This is done by parsing hiberfil.sys if present.
 
 2.1.22 - Many bug and race fixes and error handling improvements.
 

fs/ntfs/super.c

@@ -1156,6 +1156,124 @@ static BOOL load_and_check_logfile(ntfs_volume *vol)
 	return TRUE;
 }
 
+#define NTFS_HIBERFIL_HEADER_SIZE	4096
+
+/**
+ * check_windows_hibernation_status - check if Windows is suspended on a volume
+ * @vol:	ntfs super block of device to check
+ *
+ * Check if Windows is hibernated on the ntfs volume @vol.  This is done by
+ * looking for the file hiberfil.sys in the root directory of the volume.  If
+ * the file is not present Windows is definitely not suspended.
+ *
+ * If hiberfil.sys exists and is less than 4kiB in size it means Windows is
+ * definitely suspended (this volume is not the system volume).  Caveat:  on a
+ * system with many volumes it is possible that the < 4kiB check is bogus but
+ * for now this should do fine.
+ *
+ * If hiberfil.sys exists and is larger than 4kiB in size, we need to read the
+ * hiberfil header (which is the first 4kiB).  If this begins with "hibr",
+ * Windows is definitely suspended.  If it is completely full of zeroes,
+ * Windows is definitely not hibernated.  Any other case is treated as if
+ * Windows is suspended.  This caters for the above mentioned caveat of a
+ * system with many volumes where no "hibr" magic would be present and there is
+ * no zero header.
+ *
+ * Return 0 if Windows is not hibernated on the volume, >0 if Windows is
+ * hibernated on the volume, and -errno on error.
+ */
+static int check_windows_hibernation_status(ntfs_volume *vol)
+{
+	MFT_REF mref;
+	struct inode *vi;
+	ntfs_inode *ni;
+	struct page *page;
+	u32 *kaddr, *kend;
+	ntfs_name *name = NULL;
+	int ret = 1;
+	static const ntfschar hiberfil[13] = { const_cpu_to_le16('h'),
+			const_cpu_to_le16('i'), const_cpu_to_le16('b'),
+			const_cpu_to_le16('e'), const_cpu_to_le16('r'),
+			const_cpu_to_le16('f'), const_cpu_to_le16('i'),
+			const_cpu_to_le16('l'), const_cpu_to_le16('.'),
+			const_cpu_to_le16('s'), const_cpu_to_le16('y'),
+			const_cpu_to_le16('s'), 0 };
+
+	ntfs_debug("Entering.");
+	/*
+	 * Find the inode number for the hibernation file by looking up the
+	 * filename hiberfil.sys in the root directory.
+	 */
+	down(&vol->root_ino->i_sem);
+	mref = ntfs_lookup_inode_by_name(NTFS_I(vol->root_ino), hiberfil, 12,
+			&name);
+	up(&vol->root_ino->i_sem);
+	if (IS_ERR_MREF(mref)) {
+		ret = MREF_ERR(mref);
+		/* If the file does not exist, Windows is not hibernated. */
+		if (ret == -ENOENT) {
+			ntfs_debug("hiberfil.sys not present.  Windows is not "
+					"hibernated on the volume.");
+			return 0;
+		}
+		/* A real error occured. */
+		ntfs_error(vol->sb, "Failed to find inode number for "
+				"hiberfil.sys.");
+		return ret;
+	}
+	/* We do not care for the type of match that was found. */
+	kfree(name);
+	/* Get the inode. */
+	vi = ntfs_iget(vol->sb, MREF(mref));
+	if (IS_ERR(vi) || is_bad_inode(vi)) {
+		if (!IS_ERR(vi))
+			iput(vi);
+		ntfs_error(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)) {
+		ntfs_debug("hiberfil.sys is smaller than 4kiB (0x%llx).  "
+				"Windows is hibernated on the volume.  This "
+				"is not the system volume.", i_size_read(vi));
+		goto iput_out;
+	}
+	ni = NTFS_I(vi);
+	page = ntfs_map_page(vi->i_mapping, 0);
+	if (IS_ERR(page)) {
+		ntfs_error(vol->sb, "Failed to read from hiberfil.sys.");
+		ret = PTR_ERR(page);
+		goto iput_out;
+	}
+	kaddr = (u32*)page_address(page);
+	if (*(le32*)kaddr == const_cpu_to_le32(0x72626968)/*'hibr'*/) {
+		ntfs_debug("Magic \"hibr\" found in hiberfil.sys.  Windows is "
+				"hibernated on the volume.  This is the "
+				"system volume.");
+		goto unm_iput_out;
+	}
+	kend = kaddr + NTFS_HIBERFIL_HEADER_SIZE/sizeof(*kaddr);
+	do {
+		if (unlikely(*kaddr)) {
+			ntfs_debug("hiberfil.sys is larger than 4kiB "
+					"(0x%llx), does not contain the "
+					"\"hibr\" magic, and does not have a "
+					"zero header.  Windows is hibernated "
+					"on the volume.  This is not the "
+					"system volume.", i_size_read(vi));
+			goto unm_iput_out;
+		}
+	} while (++kaddr < kend);
+	ntfs_debug("hiberfil.sys contains a zero header.  Windows is not "
+			"hibernated on the volume.  This is the system "
+			"volume.");
+	ret = 0;
+unm_iput_out:
+	ntfs_unmap_page(page);
+iput_out:
+	iput(vi);
+	return ret;
+}
+
 /**
  * load_and_init_quota - load and setup the quota file for a volume if present
  * @vol:	ntfs super block describing device whose quota file to load
@@ -1570,6 +1688,9 @@ static BOOL load_system_files(ntfs_volume *vol)
 	MFT_RECORD *m;
 	VOLUME_INFORMATION *vi;
 	ntfs_attr_search_ctx *ctx;
+#ifdef NTFS_RW
+	int err;
+#endif /* NTFS_RW */
 
 	ntfs_debug("Entering.");
 #ifdef NTFS_RW
@@ -1746,6 +1867,50 @@ static BOOL load_system_files(ntfs_volume *vol)
 		/* This will prevent a read-write remount. */
 		NVolSetErrors(vol);
 	}
+#endif /* NTFS_RW */
+	/* Get the root directory inode so we can do path lookups. */
+	vol->root_ino = ntfs_iget(sb, FILE_root);
+	if (IS_ERR(vol->root_ino) || is_bad_inode(vol->root_ino)) {
+		if (!IS_ERR(vol->root_ino))
+			iput(vol->root_ino);
+		ntfs_error(sb, "Failed to load root directory.");
+		goto iput_logfile_err_out;
+	}
+#ifdef NTFS_RW
+	/*
+	 * Check if Windows is suspended to disk on the target volume.  If it
+	 * is hibernated, we must not write *anything* to the disk so set
+	 * NVolErrors() without setting the dirty volume flag and mount
+	 * read-only.  This will prevent read-write remounting and it will also
+	 * prevent all writes.
+	 */
+	err = check_windows_hibernation_status(vol);
+	if (unlikely(err)) {
+		static const char *es1a = "Failed to determine if Windows is "
+				"hibernated";
+		static const char *es1b = "Windows is hibernated";
+		static const char *es2 = ".  Run chkdsk.";
+		const char *es1;
+
+		es1 = err < 0 ? es1a : es1b;
+		/* If a read-write mount, convert it to a read-only mount. */
+		if (!(sb->s_flags & MS_RDONLY)) {
+			if (!(vol->on_errors & (ON_ERRORS_REMOUNT_RO |
+					ON_ERRORS_CONTINUE))) {
+				ntfs_error(sb, "%s and neither on_errors="
+						"continue nor on_errors="
+						"remount-ro was specified%s",
+						es1, es2);
+				goto iput_root_err_out;
+			}
+			sb->s_flags |= MS_RDONLY | MS_NOATIME | MS_NODIRATIME;
+			ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
+		} else
+			ntfs_warning(sb, "%s.  Will not be able to remount "
+					"read-write%s", es1, es2);
+		/* This will prevent a read-write remount. */
+		NVolSetErrors(vol);
+	}
 	/* If (still) a read-write mount, mark the volume dirty. */
 	if (!(sb->s_flags & MS_RDONLY) &&
 			ntfs_set_volume_flags(vol, VOLUME_IS_DIRTY)) {
@@ -1759,7 +1924,7 @@ static BOOL load_system_files(ntfs_volume *vol)
 			ntfs_error(sb, "%s and neither on_errors=continue nor "
 					"on_errors=remount-ro was specified%s",
 					es1, es2);
-			goto iput_logfile_err_out;
+			goto iput_root_err_out;
 		}
 		ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
 		sb->s_flags |= MS_RDONLY | MS_NOATIME | MS_NODIRATIME;
@@ -1786,7 +1951,7 @@ static BOOL load_system_files(ntfs_volume *vol)
 			ntfs_error(sb, "%s and neither on_errors=continue nor "
 					"on_errors=remount-ro was specified%s",
 					es1, es2);
-			goto iput_logfile_err_out;
+			goto iput_root_err_out;
 		}
 		ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
 		sb->s_flags |= MS_RDONLY | MS_NOATIME | MS_NODIRATIME;
@@ -1805,21 +1970,13 @@ static BOOL load_system_files(ntfs_volume *vol)
 			ntfs_error(sb, "%s and neither on_errors=continue nor "
 					"on_errors=remount-ro was specified%s",
 					es1, es2);
-			goto iput_logfile_err_out;
+			goto iput_root_err_out;
 		}
 		ntfs_error(sb, "%s.  Mounting read-only%s", es1, es2);
 		sb->s_flags |= MS_RDONLY | MS_NOATIME | MS_NODIRATIME;
 		NVolSetErrors(vol);
 	}
 #endif /* NTFS_RW */
-	/* Get the root directory inode. */
-	vol->root_ino = ntfs_iget(sb, FILE_root);
-	if (IS_ERR(vol->root_ino) || is_bad_inode(vol->root_ino)) {
-		if (!IS_ERR(vol->root_ino))
-			iput(vol->root_ino);
-		ntfs_error(sb, "Failed to load root directory.");
-		goto iput_logfile_err_out;
-	}
 	/* If on NTFS versions before 3.0, we are done. */
 	if (unlikely(vol->major_ver < 3))
 		return TRUE;