--- /dev/null
+/*
+ * This file is part of UBIFS.
+ *
+ * Copyright (C) 2006-2008 Nokia Corporation.
+ * Copyright (C) 2006, 2007 University of Szeged, Hungary
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * Authors: Artem Bityutskiy (Битюцкий Артём)
+ * Adrian Hunter
+ * Zoltan Sogor
+ */
+
+/*
+ * This file implements UBIFS I/O subsystem which provides various I/O-related
+ * helper functions (reading/writing/checking/validating nodes) and implements
+ * write-buffering support. Write buffers help to save space which otherwise
+ * would have been wasted for padding to the nearest minimal I/O unit boundary.
+ * Instead, data first goes to the write-buffer and is flushed when the
+ * buffer is full or when it is not used for some time (by timer). This is
+ * similar to the mechanism is used by JFFS2.
+ *
+ * Write-buffers are defined by 'struct ubifs_wbuf' objects and protected by
+ * mutexes defined inside these objects. Since sometimes upper-level code
+ * has to lock the write-buffer (e.g. journal space reservation code), many
+ * functions related to write-buffers have "nolock" suffix which means that the
+ * caller has to lock the write-buffer before calling this function.
+ *
+ * UBIFS stores nodes at 64 bit-aligned addresses. If the node length is not
+ * aligned, UBIFS starts the next node from the aligned address, and the padded
+ * bytes may contain any rubbish. In other words, UBIFS does not put padding
+ * bytes in those small gaps. Common headers of nodes store real node lengths,
+ * not aligned lengths. Indexing nodes also store real lengths in branches.
+ *
+ * UBIFS uses padding when it pads to the next min. I/O unit. In this case it
+ * uses padding nodes or padding bytes, if the padding node does not fit.
+ *
+ * All UBIFS nodes are protected by CRC checksums and UBIFS checks all nodes
+ * every time they are read from the flash media.
+ */
+
+#include "ubifs.h"
+
+/**
+ * ubifs_ro_mode - switch UBIFS to read read-only mode.
+ * @c: UBIFS file-system description object
+ * @err: error code which is the reason of switching to R/O mode
+ */
+void ubifs_ro_mode(struct ubifs_info *c, int err)
+{
+ if (!c->ro_media) {
+ c->ro_media = 1;
+ c->no_chk_data_crc = 0;
+ ubifs_warn("switched to read-only mode, error %d", err);
+ dbg_dump_stack();
+ }
+}
+
+/**
+ * ubifs_check_node - check node.
+ * @c: UBIFS file-system description object
+ * @buf: node to check
+ * @lnum: logical eraseblock number
+ * @offs: offset within the logical eraseblock
+ * @quiet: print no messages
+ * @must_chk_crc: indicates whether to always check the CRC
+ *
+ * This function checks node magic number and CRC checksum. This function also
+ * validates node length to prevent UBIFS from becoming crazy when an attacker
+ * feeds it a file-system image with incorrect nodes. For example, too large
+ * node length in the common header could cause UBIFS to read memory outside of
+ * allocated buffer when checking the CRC checksum.
+ *
+ * This function may skip data nodes CRC checking if @c->no_chk_data_crc is
+ * true, which is controlled by corresponding UBIFS mount option. However, if
+ * @must_chk_crc is true, then @c->no_chk_data_crc is ignored and CRC is
+ * checked. Similarly, if @c->always_chk_crc is true, @c->no_chk_data_crc is
+ * ignored and CRC is checked.
+ *
+ * This function returns zero in case of success and %-EUCLEAN in case of bad
+ * CRC or magic.
+ */
+int ubifs_check_node(const struct ubifs_info *c, const void *buf, int lnum,
+ int offs, int quiet, int must_chk_crc)
+{
+ int err = -EINVAL, type, node_len;
+ uint32_t crc, node_crc, magic;
+ const struct ubifs_ch *ch = buf;
+
+ ubifs_assert(lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
+ ubifs_assert(!(offs & 7) && offs < c->leb_size);
+
+ magic = le32_to_cpu(ch->magic);
+ if (magic != UBIFS_NODE_MAGIC) {
+ if (!quiet)
+ ubifs_err("bad magic %#08x, expected %#08x",
+ magic, UBIFS_NODE_MAGIC);
+ err = -EUCLEAN;
+ goto out;
+ }
+
+ type = ch->node_type;
+ if (type < 0 || type >= UBIFS_NODE_TYPES_CNT) {
+ if (!quiet)
+ ubifs_err("bad node type %d", type);
+ goto out;
+ }
+
+ node_len = le32_to_cpu(ch->len);
+ if (node_len + offs > c->leb_size)
+ goto out_len;
+
+ if (c->ranges[type].max_len == 0) {
+ if (node_len != c->ranges[type].len)
+ goto out_len;
+ } else if (node_len < c->ranges[type].min_len ||
+ node_len > c->ranges[type].max_len)
+ goto out_len;
+
+ if (!must_chk_crc && type == UBIFS_DATA_NODE && !c->always_chk_crc &&
+ c->no_chk_data_crc)
+ return 0;
+
+ crc = crc32(UBIFS_CRC32_INIT, buf + 8, node_len - 8);
+ node_crc = le32_to_cpu(ch->crc);
+ if (crc != node_crc) {
+ if (!quiet)
+ ubifs_err("bad CRC: calculated %#08x, read %#08x",
+ crc, node_crc);
+ err = -EUCLEAN;
+ goto out;
+ }
+
+ return 0;
+
+out_len:
+ if (!quiet)
+ ubifs_err("bad node length %d", node_len);
+out:
+ if (!quiet) {
+ ubifs_err("bad node at LEB %d:%d", lnum, offs);
+ dbg_dump_node(c, buf);
+ dbg_dump_stack();
+ }
+ return err;
+}
+
+/**
+ * ubifs_pad - pad flash space.
+ * @c: UBIFS file-system description object
+ * @buf: buffer to put padding to
+ * @pad: how many bytes to pad
+ *
+ * The flash media obliges us to write only in chunks of %c->min_io_size and
+ * when we have to write less data we add padding node to the write-buffer and
+ * pad it to the next minimal I/O unit's boundary. Padding nodes help when the
+ * media is being scanned. If the amount of wasted space is not enough to fit a
+ * padding node which takes %UBIFS_PAD_NODE_SZ bytes, we write padding bytes
+ * pattern (%UBIFS_PADDING_BYTE).
+ *
+ * Padding nodes are also used to fill gaps when the "commit-in-gaps" method is
+ * used.
+ */
+void ubifs_pad(const struct ubifs_info *c, void *buf, int pad)
+{
+ uint32_t crc;
+
+ ubifs_assert(pad >= 0 && !(pad & 7));
+
+ if (pad >= UBIFS_PAD_NODE_SZ) {
+ struct ubifs_ch *ch = buf;
+ struct ubifs_pad_node *pad_node = buf;
+
+ ch->magic = cpu_to_le32(UBIFS_NODE_MAGIC);
+ ch->node_type = UBIFS_PAD_NODE;
+ ch->group_type = UBIFS_NO_NODE_GROUP;
+ ch->padding[0] = ch->padding[1] = 0;
+ ch->sqnum = 0;
+ ch->len = cpu_to_le32(UBIFS_PAD_NODE_SZ);
+ pad -= UBIFS_PAD_NODE_SZ;
+ pad_node->pad_len = cpu_to_le32(pad);
+ crc = crc32(UBIFS_CRC32_INIT, buf + 8, UBIFS_PAD_NODE_SZ - 8);
+ ch->crc = cpu_to_le32(crc);
+ memset(buf + UBIFS_PAD_NODE_SZ, 0, pad);
+ } else if (pad > 0)
+ /* Too little space, padding node won't fit */
+ memset(buf, UBIFS_PADDING_BYTE, pad);
+}
+
+/**
+ * next_sqnum - get next sequence number.
+ * @c: UBIFS file-system description object
+ */
+static unsigned long long next_sqnum(struct ubifs_info *c)
+{
+ unsigned long long sqnum;
+
+ spin_lock(&c->cnt_lock);
+ sqnum = ++c->max_sqnum;
+ spin_unlock(&c->cnt_lock);
+
+ if (unlikely(sqnum >= SQNUM_WARN_WATERMARK)) {
+ if (sqnum >= SQNUM_WATERMARK) {
+ ubifs_err("sequence number overflow %llu, end of life",
+ sqnum);
+ ubifs_ro_mode(c, -EINVAL);
+ }
+ ubifs_warn("running out of sequence numbers, end of life soon");
+ }
+
+ return sqnum;
+}
+
+/**
+ * ubifs_prepare_node - prepare node to be written to flash.
+ * @c: UBIFS file-system description object
+ * @node: the node to pad
+ * @len: node length
+ * @pad: if the buffer has to be padded
+ *
+ * This function prepares node at @node to be written to the media - it
+ * calculates node CRC, fills the common header, and adds proper padding up to
+ * the next minimum I/O unit if @pad is not zero.
+ */
+void ubifs_prepare_node(struct ubifs_info *c, void *node, int len, int pad)
+{
+ uint32_t crc;
+ struct ubifs_ch *ch = node;
+ unsigned long long sqnum = next_sqnum(c);
+
+ ubifs_assert(len >= UBIFS_CH_SZ);
+
+ ch->magic = cpu_to_le32(UBIFS_NODE_MAGIC);
+ ch->len = cpu_to_le32(len);
+ ch->group_type = UBIFS_NO_NODE_GROUP;
+ ch->sqnum = cpu_to_le64(sqnum);
+ ch->padding[0] = ch->padding[1] = 0;
+ crc = crc32(UBIFS_CRC32_INIT, node + 8, len - 8);
+ ch->crc = cpu_to_le32(crc);
+
+ if (pad) {
+ len = ALIGN(len, 8);
+ pad = ALIGN(len, c->min_io_size) - len;
+ ubifs_pad(c, node + len, pad);
+ }
+}
+
+/**
+ * ubifs_read_node - read node.
+ * @c: UBIFS file-system description object
+ * @buf: buffer to read to
+ * @type: node type
+ * @len: node length (not aligned)
+ * @lnum: logical eraseblock number
+ * @offs: offset within the logical eraseblock
+ *
+ * This function reads a node of known type and and length, checks it and
+ * stores in @buf. Returns zero in case of success, %-EUCLEAN if CRC mismatched
+ * and a negative error code in case of failure.
+ */
+int ubifs_read_node(const struct ubifs_info *c, void *buf, int type, int len,
+ int lnum, int offs)
+{
+ int err, l;
+ struct ubifs_ch *ch = buf;
+
+ dbg_io("LEB %d:%d, %s, length %d", lnum, offs, dbg_ntype(type), len);
+ ubifs_assert(lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
+ ubifs_assert(len >= UBIFS_CH_SZ && offs + len <= c->leb_size);
+ ubifs_assert(!(offs & 7) && offs < c->leb_size);
+ ubifs_assert(type >= 0 && type < UBIFS_NODE_TYPES_CNT);
+
+ err = ubi_read(c->ubi, lnum, buf, offs, len);
+ if (err && err != -EBADMSG) {
+ ubifs_err("cannot read node %d from LEB %d:%d, error %d",
+ type, lnum, offs, err);
+ return err;
+ }
+
+ if (type != ch->node_type) {
+ ubifs_err("bad node type (%d but expected %d)",
+ ch->node_type, type);
+ goto out;
+ }
+
+ err = ubifs_check_node(c, buf, lnum, offs, 0, 0);
+ if (err) {
+ ubifs_err("expected node type %d", type);
+ return err;
+ }
+
+ l = le32_to_cpu(ch->len);
+ if (l != len) {
+ ubifs_err("bad node length %d, expected %d", l, len);
+ goto out;
+ }
+
+ return 0;
+
+out:
+ ubifs_err("bad node at LEB %d:%d", lnum, offs);
+ dbg_dump_node(c, buf);
+ dbg_dump_stack();
+ return -EINVAL;
+}
Code Review / kvmfornfv.git / blobdiff