Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 956 insertions, 0 deletions

diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
new file mode 100644
index 0000000000..e7693b94e5
--- /dev/null
+++ b/fs/ubifs/sb.c
@@ -0,0 +1,956 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * This file is part of UBIFS.
+ *
+ * Copyright (C) 2006-2008 Nokia Corporation.
+ *
+ * Authors: Artem Bityutskiy (Битюцкий Артём)
+ *          Adrian Hunter
+ */
+
+/*
+ * This file implements UBIFS superblock. The superblock is stored at the first
+ * LEB of the volume and is never changed by UBIFS. Only user-space tools may
+ * change it. The superblock node mostly contains geometry information.
+ */
+
+#include "ubifs.h"
+#include <linux/slab.h>
+#include <linux/math64.h>
+#include <linux/uuid.h>
+
+/*
+ * Default journal size in logical eraseblocks as a percent of total
+ * flash size.
+ */
+#define DEFAULT_JNL_PERCENT 5
+
+/* Default maximum journal size in bytes */
+#define DEFAULT_MAX_JNL (32*1024*1024)
+
+/* Default indexing tree fanout */
+#define DEFAULT_FANOUT 8
+
+/* Default number of data journal heads */
+#define DEFAULT_JHEADS_CNT 1
+
+/* Default positions of different LEBs in the main area */
+#define DEFAULT_IDX_LEB  0
+#define DEFAULT_DATA_LEB 1
+#define DEFAULT_GC_LEB   2
+
+/* Default number of LEB numbers in LPT's save table */
+#define DEFAULT_LSAVE_CNT 256
+
+/* Default reserved pool size as a percent of maximum free space */
+#define DEFAULT_RP_PERCENT 5
+
+/* The default maximum size of reserved pool in bytes */
+#define DEFAULT_MAX_RP_SIZE (5*1024*1024)
+
+/* Default time granularity in nanoseconds */
+#define DEFAULT_TIME_GRAN 1000000000
+
+static int get_default_compressor(struct ubifs_info *c)
+{
+	if (ubifs_compr_present(c, UBIFS_COMPR_ZSTD))
+		return UBIFS_COMPR_ZSTD;
+
+	if (ubifs_compr_present(c, UBIFS_COMPR_LZO))
+		return UBIFS_COMPR_LZO;
+
+	if (ubifs_compr_present(c, UBIFS_COMPR_ZLIB))
+		return UBIFS_COMPR_ZLIB;
+
+	return UBIFS_COMPR_NONE;
+}
+
+/**
+ * create_default_filesystem - format empty UBI volume.
+ * @c: UBIFS file-system description object
+ *
+ * This function creates default empty file-system. Returns zero in case of
+ * success and a negative error code in case of failure.
+ */
+static int create_default_filesystem(struct ubifs_info *c)
+{
+	struct ubifs_sb_node *sup;
+	struct ubifs_mst_node *mst;
+	struct ubifs_idx_node *idx;
+	struct ubifs_branch *br;
+	struct ubifs_ino_node *ino;
+	struct ubifs_cs_node *cs;
+	union ubifs_key key;
+	int err, tmp, jnl_lebs, log_lebs, max_buds, main_lebs, main_first;
+	int lpt_lebs, lpt_first, orph_lebs, big_lpt, ino_waste, sup_flags = 0;
+	int min_leb_cnt = UBIFS_MIN_LEB_CNT;
+	int idx_node_size;
+	long long tmp64, main_bytes;
+	__le64 tmp_le64;
+	struct timespec64 ts;
+	u8 hash[UBIFS_HASH_ARR_SZ];
+	u8 hash_lpt[UBIFS_HASH_ARR_SZ];
+
+	/* Some functions called from here depend on the @c->key_len filed */
+	c->key_len = UBIFS_SK_LEN;
+
+	/*
+	 * First of all, we have to calculate default file-system geometry -
+	 * log size, journal size, etc.
+	 */
+	if (c->leb_cnt < 0x7FFFFFFF / DEFAULT_JNL_PERCENT)
+		/* We can first multiply then divide and have no overflow */
+		jnl_lebs = c->leb_cnt * DEFAULT_JNL_PERCENT / 100;
+	else
+		jnl_lebs = (c->leb_cnt / 100) * DEFAULT_JNL_PERCENT;
+
+	if (jnl_lebs < UBIFS_MIN_JNL_LEBS)
+		jnl_lebs = UBIFS_MIN_JNL_LEBS;
+	if (jnl_lebs * c->leb_size > DEFAULT_MAX_JNL)
+		jnl_lebs = DEFAULT_MAX_JNL / c->leb_size;
+
+	/*
+	 * The log should be large enough to fit reference nodes for all bud
+	 * LEBs. Because buds do not have to start from the beginning of LEBs
+	 * (half of the LEB may contain committed data), the log should
+	 * generally be larger, make it twice as large.
+	 */
+	tmp = 2 * (c->ref_node_alsz * jnl_lebs) + c->leb_size - 1;
+	log_lebs = tmp / c->leb_size;
+	/* Plus one LEB reserved for commit */
+	log_lebs += 1;
+	if (c->leb_cnt - min_leb_cnt > 8) {
+		/* And some extra space to allow writes while committing */
+		log_lebs += 1;
+		min_leb_cnt += 1;
+	}
+
+	max_buds = jnl_lebs - log_lebs;
+	if (max_buds < UBIFS_MIN_BUD_LEBS)
+		max_buds = UBIFS_MIN_BUD_LEBS;
+
+	/*
+	 * Orphan nodes are stored in a separate area. One node can store a lot
+	 * of orphan inode numbers, but when new orphan comes we just add a new
+	 * orphan node. At some point the nodes are consolidated into one
+	 * orphan node.
+	 */
+	orph_lebs = UBIFS_MIN_ORPH_LEBS;
+	if (c->leb_cnt - min_leb_cnt > 1)
+		/*
+		 * For debugging purposes it is better to have at least 2
+		 * orphan LEBs, because the orphan subsystem would need to do
+		 * consolidations and would be stressed more.
+		 */
+		orph_lebs += 1;
+
+	main_lebs = c->leb_cnt - UBIFS_SB_LEBS - UBIFS_MST_LEBS - log_lebs;
+	main_lebs -= orph_lebs;
+
+	lpt_first = UBIFS_LOG_LNUM + log_lebs;
+	c->lsave_cnt = DEFAULT_LSAVE_CNT;
+	c->max_leb_cnt = c->leb_cnt;
+	err = ubifs_create_dflt_lpt(c, &main_lebs, lpt_first, &lpt_lebs,
+				    &big_lpt, hash_lpt);
+	if (err)
+		return err;
+
+	dbg_gen("LEB Properties Tree created (LEBs %d-%d)", lpt_first,
+		lpt_first + lpt_lebs - 1);
+
+	main_first = c->leb_cnt - main_lebs;
+
+	sup = kzalloc(ALIGN(UBIFS_SB_NODE_SZ, c->min_io_size), GFP_KERNEL);
+	mst = kzalloc(c->mst_node_alsz, GFP_KERNEL);
+	idx_node_size = ubifs_idx_node_sz(c, 1);
+	idx = kzalloc(ALIGN(idx_node_size, c->min_io_size), GFP_KERNEL);
+	ino = kzalloc(ALIGN(UBIFS_INO_NODE_SZ, c->min_io_size), GFP_KERNEL);
+	cs = kzalloc(ALIGN(UBIFS_CS_NODE_SZ, c->min_io_size), GFP_KERNEL);
+
+	if (!sup || !mst || !idx || !ino || !cs) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	/* Create default superblock */
+
+	tmp64 = (long long)max_buds * c->leb_size;
+	if (big_lpt)
+		sup_flags |= UBIFS_FLG_BIGLPT;
+	if (ubifs_default_version > 4)
+		sup_flags |= UBIFS_FLG_DOUBLE_HASH;
+
+	if (ubifs_authenticated(c)) {
+		sup_flags |= UBIFS_FLG_AUTHENTICATION;
+		sup->hash_algo = cpu_to_le16(c->auth_hash_algo);
+		err = ubifs_hmac_wkm(c, sup->hmac_wkm);
+		if (err)
+			goto out;
+	} else {
+		sup->hash_algo = cpu_to_le16(0xffff);
+	}
+
+	sup->ch.node_type  = UBIFS_SB_NODE;
+	sup->key_hash      = UBIFS_KEY_HASH_R5;
+	sup->flags         = cpu_to_le32(sup_flags);
+	sup->min_io_size   = cpu_to_le32(c->min_io_size);
+	sup->leb_size      = cpu_to_le32(c->leb_size);
+	sup->leb_cnt       = cpu_to_le32(c->leb_cnt);
+	sup->max_leb_cnt   = cpu_to_le32(c->max_leb_cnt);
+	sup->max_bud_bytes = cpu_to_le64(tmp64);
+	sup->log_lebs      = cpu_to_le32(log_lebs);
+	sup->lpt_lebs      = cpu_to_le32(lpt_lebs);
+	sup->orph_lebs     = cpu_to_le32(orph_lebs);
+	sup->jhead_cnt     = cpu_to_le32(DEFAULT_JHEADS_CNT);
+	sup->fanout        = cpu_to_le32(DEFAULT_FANOUT);
+	sup->lsave_cnt     = cpu_to_le32(c->lsave_cnt);
+	sup->fmt_version   = cpu_to_le32(ubifs_default_version);
+	sup->time_gran     = cpu_to_le32(DEFAULT_TIME_GRAN);
+	if (c->mount_opts.override_compr)
+		sup->default_compr = cpu_to_le16(c->mount_opts.compr_type);
+	else
+		sup->default_compr = cpu_to_le16(get_default_compressor(c));
+
+	generate_random_uuid(sup->uuid);
+
+	main_bytes = (long long)main_lebs * c->leb_size;
+	tmp64 = div_u64(main_bytes * DEFAULT_RP_PERCENT, 100);
+	if (tmp64 > DEFAULT_MAX_RP_SIZE)
+		tmp64 = DEFAULT_MAX_RP_SIZE;
+	sup->rp_size = cpu_to_le64(tmp64);
+	sup->ro_compat_version = cpu_to_le32(UBIFS_RO_COMPAT_VERSION);
+
+	dbg_gen("default superblock created at LEB 0:0");
+
+	/* Create default master node */
+
+	mst->ch.node_type = UBIFS_MST_NODE;
+	mst->log_lnum     = cpu_to_le32(UBIFS_LOG_LNUM);
+	mst->highest_inum = cpu_to_le64(UBIFS_FIRST_INO);
+	mst->cmt_no       = 0;
+	mst->root_lnum    = cpu_to_le32(main_first + DEFAULT_IDX_LEB);
+	mst->root_offs    = 0;
+	tmp = ubifs_idx_node_sz(c, 1);
+	mst->root_len     = cpu_to_le32(tmp);
+	mst->gc_lnum      = cpu_to_le32(main_first + DEFAULT_GC_LEB);
+	mst->ihead_lnum   = cpu_to_le32(main_first + DEFAULT_IDX_LEB);
+	mst->ihead_offs   = cpu_to_le32(ALIGN(tmp, c->min_io_size));
+	mst->index_size   = cpu_to_le64(ALIGN(tmp, 8));
+	mst->lpt_lnum     = cpu_to_le32(c->lpt_lnum);
+	mst->lpt_offs     = cpu_to_le32(c->lpt_offs);
+	mst->nhead_lnum   = cpu_to_le32(c->nhead_lnum);
+	mst->nhead_offs   = cpu_to_le32(c->nhead_offs);
+	mst->ltab_lnum    = cpu_to_le32(c->ltab_lnum);
+	mst->ltab_offs    = cpu_to_le32(c->ltab_offs);
+	mst->lsave_lnum   = cpu_to_le32(c->lsave_lnum);
+	mst->lsave_offs   = cpu_to_le32(c->lsave_offs);
+	mst->lscan_lnum   = cpu_to_le32(main_first);
+	mst->empty_lebs   = cpu_to_le32(main_lebs - 2);
+	mst->idx_lebs     = cpu_to_le32(1);
+	mst->leb_cnt      = cpu_to_le32(c->leb_cnt);
+	ubifs_copy_hash(c, hash_lpt, mst->hash_lpt);
+
+	/* Calculate lprops statistics */
+	tmp64 = main_bytes;
+	tmp64 -= ALIGN(ubifs_idx_node_sz(c, 1), c->min_io_size);
+	tmp64 -= ALIGN(UBIFS_INO_NODE_SZ, c->min_io_size);
+	mst->total_free = cpu_to_le64(tmp64);
+
+	tmp64 = ALIGN(ubifs_idx_node_sz(c, 1), c->min_io_size);
+	ino_waste = ALIGN(UBIFS_INO_NODE_SZ, c->min_io_size) -
+			  UBIFS_INO_NODE_SZ;
+	tmp64 += ino_waste;
+	tmp64 -= ALIGN(ubifs_idx_node_sz(c, 1), 8);
+	mst->total_dirty = cpu_to_le64(tmp64);
+
+	/*  The indexing LEB does not contribute to dark space */
+	tmp64 = ((long long)(c->main_lebs - 1) * c->dark_wm);
+	mst->total_dark = cpu_to_le64(tmp64);
+
+	mst->total_used = cpu_to_le64(UBIFS_INO_NODE_SZ);
+
+	dbg_gen("default master node created at LEB %d:0", UBIFS_MST_LNUM);
+
+	/* Create the root indexing node */
+
+	c->key_fmt = UBIFS_SIMPLE_KEY_FMT;
+	c->key_hash = key_r5_hash;
+
+	idx->ch.node_type = UBIFS_IDX_NODE;
+	idx->child_cnt = cpu_to_le16(1);
+	ino_key_init(c, &key, UBIFS_ROOT_INO);
+	br = ubifs_idx_branch(c, idx, 0);
+	key_write_idx(c, &key, &br->key);
+	br->lnum = cpu_to_le32(main_first + DEFAULT_DATA_LEB);
+	br->len  = cpu_to_le32(UBIFS_INO_NODE_SZ);
+
+	dbg_gen("default root indexing node created LEB %d:0",
+		main_first + DEFAULT_IDX_LEB);
+
+	/* Create default root inode */
+
+	ino_key_init_flash(c, &ino->key, UBIFS_ROOT_INO);
+	ino->ch.node_type = UBIFS_INO_NODE;
+	ino->creat_sqnum = cpu_to_le64(++c->max_sqnum);
+	ino->nlink = cpu_to_le32(2);
+
+	ktime_get_coarse_real_ts64(&ts);
+	tmp_le64 = cpu_to_le64(ts.tv_sec);
+	ino->atime_sec   = tmp_le64;
+	ino->ctime_sec   = tmp_le64;
+	ino->mtime_sec   = tmp_le64;
+	ino->atime_nsec  = 0;
+	ino->ctime_nsec  = 0;
+	ino->mtime_nsec  = 0;
+	ino->mode = cpu_to_le32(S_IFDIR | S_IRUGO | S_IWUSR | S_IXUGO);
+	ino->size = cpu_to_le64(UBIFS_INO_NODE_SZ);
+
+	/* Set compression enabled by default */
+	ino->flags = cpu_to_le32(UBIFS_COMPR_FL);
+
+	dbg_gen("root inode created at LEB %d:0",
+		main_first + DEFAULT_DATA_LEB);
+
+	/*
+	 * The first node in the log has to be the commit start node. This is
+	 * always the case during normal file-system operation. Write a fake
+	 * commit start node to the log.
+	 */
+
+	cs->ch.node_type = UBIFS_CS_NODE;
+
+	err = ubifs_write_node_hmac(c, sup, UBIFS_SB_NODE_SZ, 0, 0,
+				    offsetof(struct ubifs_sb_node, hmac));
+	if (err)
+		goto out;
+
+	err = ubifs_write_node(c, ino, UBIFS_INO_NODE_SZ,
+			       main_first + DEFAULT_DATA_LEB, 0);
+	if (err)
+		goto out;
+
+	ubifs_node_calc_hash(c, ino, hash);
+	ubifs_copy_hash(c, hash, ubifs_branch_hash(c, br));
+
+	err = ubifs_write_node(c, idx, idx_node_size, main_first + DEFAULT_IDX_LEB, 0);
+	if (err)
+		goto out;
+
+	ubifs_node_calc_hash(c, idx, hash);
+	ubifs_copy_hash(c, hash, mst->hash_root_idx);
+
+	err = ubifs_write_node_hmac(c, mst, UBIFS_MST_NODE_SZ, UBIFS_MST_LNUM, 0,
+		offsetof(struct ubifs_mst_node, hmac));
+	if (err)
+		goto out;
+
+	err = ubifs_write_node_hmac(c, mst, UBIFS_MST_NODE_SZ, UBIFS_MST_LNUM + 1,
+			       0, offsetof(struct ubifs_mst_node, hmac));
+	if (err)
+		goto out;
+
+	err = ubifs_write_node(c, cs, UBIFS_CS_NODE_SZ, UBIFS_LOG_LNUM, 0);
+	if (err)
+		goto out;
+
+	ubifs_msg(c, "default file-system created");
+
+	err = 0;
+out:
+	kfree(sup);
+	kfree(mst);
+	kfree(idx);
+	kfree(ino);
+	kfree(cs);
+
+	return err;
+}
+
+/**
+ * validate_sb - validate superblock node.
+ * @c: UBIFS file-system description object
+ * @sup: superblock node
+ *
+ * This function validates superblock node @sup. Since most of data was read
+ * from the superblock and stored in @c, the function validates fields in @c
+ * instead. Returns zero in case of success and %-EINVAL in case of validation
+ * failure.
+ */
+static int validate_sb(struct ubifs_info *c, struct ubifs_sb_node *sup)
+{
+	long long max_bytes;
+	int err = 1, min_leb_cnt;
+
+	if (!c->key_hash) {
+		err = 2;
+		goto failed;
+	}
+
+	if (sup->key_fmt != UBIFS_SIMPLE_KEY_FMT) {
+		err = 3;
+		goto failed;
+	}
+
+	if (le32_to_cpu(sup->min_io_size) != c->min_io_size) {
+		ubifs_err(c, "min. I/O unit mismatch: %d in superblock, %d real",
+			  le32_to_cpu(sup->min_io_size), c->min_io_size);
+		goto failed;
+	}
+
+	if (le32_to_cpu(sup->leb_size) != c->leb_size) {
+		ubifs_err(c, "LEB size mismatch: %d in superblock, %d real",
+			  le32_to_cpu(sup->leb_size), c->leb_size);
+		goto failed;
+	}
+
+	if (c->log_lebs < UBIFS_MIN_LOG_LEBS ||
+	    c->lpt_lebs < UBIFS_MIN_LPT_LEBS ||
+	    c->orph_lebs < UBIFS_MIN_ORPH_LEBS ||
+	    c->main_lebs < UBIFS_MIN_MAIN_LEBS) {
+		err = 4;
+		goto failed;
+	}
+
+	/*
+	 * Calculate minimum allowed amount of main area LEBs. This is very
+	 * similar to %UBIFS_MIN_LEB_CNT, but we take into account real what we
+	 * have just read from the superblock.
+	 */
+	min_leb_cnt = UBIFS_SB_LEBS + UBIFS_MST_LEBS + c->log_lebs;
+	min_leb_cnt += c->lpt_lebs + c->orph_lebs + c->jhead_cnt + 6;
+
+	if (c->leb_cnt < min_leb_cnt || c->leb_cnt > c->vi.size) {
+		ubifs_err(c, "bad LEB count: %d in superblock, %d on UBI volume, %d minimum required",
+			  c->leb_cnt, c->vi.size, min_leb_cnt);
+		goto failed;
+	}
+
+	if (c->max_leb_cnt < c->leb_cnt) {
+		ubifs_err(c, "max. LEB count %d less than LEB count %d",
+			  c->max_leb_cnt, c->leb_cnt);
+		goto failed;
+	}
+
+	if (c->main_lebs < UBIFS_MIN_MAIN_LEBS) {
+		ubifs_err(c, "too few main LEBs count %d, must be at least %d",
+			  c->main_lebs, UBIFS_MIN_MAIN_LEBS);
+		goto failed;
+	}
+
+	max_bytes = (long long)c->leb_size * UBIFS_MIN_BUD_LEBS;
+	if (c->max_bud_bytes < max_bytes) {
+		ubifs_err(c, "too small journal (%lld bytes), must be at least %lld bytes",
+			  c->max_bud_bytes, max_bytes);
+		goto failed;
+	}
+
+	max_bytes = (long long)c->leb_size * c->main_lebs;
+	if (c->max_bud_bytes > max_bytes) {
+		ubifs_err(c, "too large journal size (%lld bytes), only %lld bytes available in the main area",
+			  c->max_bud_bytes, max_bytes);
+		goto failed;
+	}
+
+	if (c->jhead_cnt < NONDATA_JHEADS_CNT + 1 ||
+	    c->jhead_cnt > NONDATA_JHEADS_CNT + UBIFS_MAX_JHEADS) {
+		err = 9;
+		goto failed;
+	}
+
+	if (c->fanout < UBIFS_MIN_FANOUT ||
+	    ubifs_idx_node_sz(c, c->fanout) > c->leb_size) {
+		err = 10;
+		goto failed;
+	}
+
+	if (c->lsave_cnt < 0 || (c->lsave_cnt > DEFAULT_LSAVE_CNT &&
+	    c->lsave_cnt > c->max_leb_cnt - UBIFS_SB_LEBS - UBIFS_MST_LEBS -
+	    c->log_lebs - c->lpt_lebs - c->orph_lebs)) {
+		err = 11;
+		goto failed;
+	}
+
+	if (UBIFS_SB_LEBS + UBIFS_MST_LEBS + c->log_lebs + c->lpt_lebs +
+	    c->orph_lebs + c->main_lebs != c->leb_cnt) {
+		err = 12;
+		goto failed;
+	}
+
+	if (c->default_compr >= UBIFS_COMPR_TYPES_CNT) {
+		err = 13;
+		goto failed;
+	}
+
+	if (c->rp_size < 0 || max_bytes < c->rp_size) {
+		err = 14;
+		goto failed;
+	}
+
+	if (le32_to_cpu(sup->time_gran) > 1000000000 ||
+	    le32_to_cpu(sup->time_gran) < 1) {
+		err = 15;
+		goto failed;
+	}
+
+	if (!c->double_hash && c->fmt_version >= 5) {
+		err = 16;
+		goto failed;
+	}
+
+	if (c->encrypted && c->fmt_version < 5) {
+		err = 17;
+		goto failed;
+	}
+
+	return 0;
+
+failed:
+	ubifs_err(c, "bad superblock, error %d", err);
+	ubifs_dump_node(c, sup, ALIGN(UBIFS_SB_NODE_SZ, c->min_io_size));
+	return -EINVAL;
+}
+
+/**
+ * ubifs_read_sb_node - read superblock node.
+ * @c: UBIFS file-system description object
+ *
+ * This function returns a pointer to the superblock node or a negative error
+ * code. Note, the user of this function is responsible of kfree()'ing the
+ * returned superblock buffer.
+ */
+static struct ubifs_sb_node *ubifs_read_sb_node(struct ubifs_info *c)
+{
+	struct ubifs_sb_node *sup;
+	int err;
+
+	sup = kmalloc(ALIGN(UBIFS_SB_NODE_SZ, c->min_io_size), GFP_NOFS);
+	if (!sup)
+		return ERR_PTR(-ENOMEM);
+
+	err = ubifs_read_node(c, sup, UBIFS_SB_NODE, UBIFS_SB_NODE_SZ,
+			      UBIFS_SB_LNUM, 0);
+	if (err) {
+		kfree(sup);
+		return ERR_PTR(err);
+	}
+
+	return sup;
+}
+
+static int authenticate_sb_node(struct ubifs_info *c,
+				const struct ubifs_sb_node *sup)
+{
+	unsigned int sup_flags = le32_to_cpu(sup->flags);
+	u8 hmac_wkm[UBIFS_HMAC_ARR_SZ];
+	int authenticated = !!(sup_flags & UBIFS_FLG_AUTHENTICATION);
+	int hash_algo;
+	int err;
+
+	if (c->authenticated && !authenticated) {
+		ubifs_err(c, "authenticated FS forced, but found FS without authentication");
+		return -EINVAL;
+	}
+
+	if (!c->authenticated && authenticated) {
+		ubifs_err(c, "authenticated FS found, but no key given");
+		return -EINVAL;
+	}
+
+	ubifs_msg(c, "Mounting in %sauthenticated mode",
+		  c->authenticated ? "" : "un");
+
+	if (!c->authenticated)
+		return 0;
+
+	if (!IS_ENABLED(CONFIG_UBIFS_FS_AUTHENTICATION))
+		return -EOPNOTSUPP;
+
+	hash_algo = le16_to_cpu(sup->hash_algo);
+	if (hash_algo >= HASH_ALGO__LAST) {
+		ubifs_err(c, "superblock uses unknown hash algo %d",
+			  hash_algo);
+		return -EINVAL;
+	}
+
+	if (strcmp(hash_algo_name[hash_algo], c->auth_hash_name)) {
+		ubifs_err(c, "This filesystem uses %s for hashing,"
+			     " but %s is specified", hash_algo_name[hash_algo],
+			     c->auth_hash_name);
+		return -EINVAL;
+	}
+
+	/*
+	 * The super block node can either be authenticated by a HMAC or
+	 * by a signature in a ubifs_sig_node directly following the
+	 * super block node to support offline image creation.
+	 */
+	if (ubifs_hmac_zero(c, sup->hmac)) {
+		err = ubifs_sb_verify_signature(c, sup);
+	} else {
+		err = ubifs_hmac_wkm(c, hmac_wkm);
+		if (err)
+			return err;
+		if (ubifs_check_hmac(c, hmac_wkm, sup->hmac_wkm)) {
+			ubifs_err(c, "provided key does not fit");
+			return -ENOKEY;
+		}
+		err = ubifs_node_verify_hmac(c, sup, sizeof(*sup),
+					     offsetof(struct ubifs_sb_node,
+						      hmac));
+	}
+
+	if (err)
+		ubifs_err(c, "Failed to authenticate superblock: %d", err);
+
+	return err;
+}
+
+/**
+ * ubifs_write_sb_node - write superblock node.
+ * @c: UBIFS file-system description object
+ * @sup: superblock node read with 'ubifs_read_sb_node()'
+ *
+ * This function returns %0 on success and a negative error code on failure.
+ */
+int ubifs_write_sb_node(struct ubifs_info *c, struct ubifs_sb_node *sup)
+{
+	int len = ALIGN(UBIFS_SB_NODE_SZ, c->min_io_size);
+	int err;
+
+	err = ubifs_prepare_node_hmac(c, sup, UBIFS_SB_NODE_SZ,
+				      offsetof(struct ubifs_sb_node, hmac), 1);
+	if (err)
+		return err;
+
+	return ubifs_leb_change(c, UBIFS_SB_LNUM, sup, len);
+}
+
+/**
+ * ubifs_read_superblock - read superblock.
+ * @c: UBIFS file-system description object
+ *
+ * This function finds, reads and checks the superblock. If an empty UBI volume
+ * is being mounted, this function creates default superblock. Returns zero in
+ * case of success, and a negative error code in case of failure.
+ */
+int ubifs_read_superblock(struct ubifs_info *c)
+{
+	int err, sup_flags;
+	struct ubifs_sb_node *sup;
+
+	if (c->empty) {
+		err = create_default_filesystem(c);
+		if (err)
+			return err;
+	}
+
+	sup = ubifs_read_sb_node(c);
+	if (IS_ERR(sup))
+		return PTR_ERR(sup);
+
+	c->sup_node = sup;
+
+	c->fmt_version = le32_to_cpu(sup->fmt_version);
+	c->ro_compat_version = le32_to_cpu(sup->ro_compat_version);
+
+	/*
+	 * The software supports all previous versions but not future versions,
+	 * due to the unavailability of time-travelling equipment.
+	 */
+	if (c->fmt_version > UBIFS_FORMAT_VERSION) {
+		ubifs_assert(c, !c->ro_media || c->ro_mount);
+		if (!c->ro_mount ||
+		    c->ro_compat_version > UBIFS_RO_COMPAT_VERSION) {
+			ubifs_err(c, "on-flash format version is w%d/r%d, but software only supports up to version w%d/r%d",
+				  c->fmt_version, c->ro_compat_version,
+				  UBIFS_FORMAT_VERSION,
+				  UBIFS_RO_COMPAT_VERSION);
+			if (c->ro_compat_version <= UBIFS_RO_COMPAT_VERSION) {
+				ubifs_msg(c, "only R/O mounting is possible");
+				err = -EROFS;
+			} else
+				err = -EINVAL;
+			goto out;
+		}
+
+		/*
+		 * The FS is mounted R/O, and the media format is
+		 * R/O-compatible with the UBIFS implementation, so we can
+		 * mount.
+		 */
+		c->rw_incompat = 1;
+	}
+
+	if (c->fmt_version < 3) {
+		ubifs_err(c, "on-flash format version %d is not supported",
+			  c->fmt_version);
+		err = -EINVAL;
+		goto out;
+	}
+
+	switch (sup->key_hash) {
+	case UBIFS_KEY_HASH_R5:
+		c->key_hash = key_r5_hash;
+		c->key_hash_type = UBIFS_KEY_HASH_R5;
+		break;
+
+	case UBIFS_KEY_HASH_TEST:
+		c->key_hash = key_test_hash;
+		c->key_hash_type = UBIFS_KEY_HASH_TEST;
+		break;
+	}
+
+	c->key_fmt = sup->key_fmt;
+
+	switch (c->key_fmt) {
+	case UBIFS_SIMPLE_KEY_FMT:
+		c->key_len = UBIFS_SK_LEN;
+		break;
+	default:
+		ubifs_err(c, "unsupported key format");
+		err = -EINVAL;
+		goto out;
+	}
+
+	c->leb_cnt       = le32_to_cpu(sup->leb_cnt);
+	c->max_leb_cnt   = le32_to_cpu(sup->max_leb_cnt);
+	c->max_bud_bytes = le64_to_cpu(sup->max_bud_bytes);
+	c->log_lebs      = le32_to_cpu(sup->log_lebs);
+	c->lpt_lebs      = le32_to_cpu(sup->lpt_lebs);
+	c->orph_lebs     = le32_to_cpu(sup->orph_lebs);
+	c->jhead_cnt     = le32_to_cpu(sup->jhead_cnt) + NONDATA_JHEADS_CNT;
+	c->fanout        = le32_to_cpu(sup->fanout);
+	c->lsave_cnt     = le32_to_cpu(sup->lsave_cnt);
+	c->rp_size       = le64_to_cpu(sup->rp_size);
+	c->rp_uid        = make_kuid(&init_user_ns, le32_to_cpu(sup->rp_uid));
+	c->rp_gid        = make_kgid(&init_user_ns, le32_to_cpu(sup->rp_gid));
+	sup_flags        = le32_to_cpu(sup->flags);
+	if (!c->mount_opts.override_compr)
+		c->default_compr = le16_to_cpu(sup->default_compr);
+
+	c->vfs_sb->s_time_gran = le32_to_cpu(sup->time_gran);
+	memcpy(&c->uuid, &sup->uuid, 16);
+	c->big_lpt = !!(sup_flags & UBIFS_FLG_BIGLPT);
+	c->space_fixup = !!(sup_flags & UBIFS_FLG_SPACE_FIXUP);
+	c->double_hash = !!(sup_flags & UBIFS_FLG_DOUBLE_HASH);
+	c->encrypted = !!(sup_flags & UBIFS_FLG_ENCRYPTION);
+
+	err = authenticate_sb_node(c, sup);
+	if (err)
+		goto out;
+
+	if ((sup_flags & ~UBIFS_FLG_MASK) != 0) {
+		ubifs_err(c, "Unknown feature flags found: %#x",
+			  sup_flags & ~UBIFS_FLG_MASK);
+		err = -EINVAL;
+		goto out;
+	}
+
+	if (!IS_ENABLED(CONFIG_FS_ENCRYPTION) && c->encrypted) {
+		ubifs_err(c, "file system contains encrypted files but UBIFS"
+			     " was built without crypto support.");
+		err = -EINVAL;
+		goto out;
+	}
+
+	/* Automatically increase file system size to the maximum size */
+	if (c->leb_cnt < c->vi.size && c->leb_cnt < c->max_leb_cnt) {
+		int old_leb_cnt = c->leb_cnt;
+
+		c->leb_cnt = min_t(int, c->max_leb_cnt, c->vi.size);
+		sup->leb_cnt = cpu_to_le32(c->leb_cnt);
+
+		c->superblock_need_write = 1;
+
+		dbg_mnt("Auto resizing from %d LEBs to %d LEBs",
+			old_leb_cnt, c->leb_cnt);
+	}
+
+	c->log_bytes = (long long)c->log_lebs * c->leb_size;
+	c->log_last = UBIFS_LOG_LNUM + c->log_lebs - 1;
+	c->lpt_first = UBIFS_LOG_LNUM + c->log_lebs;
+	c->lpt_last = c->lpt_first + c->lpt_lebs - 1;
+	c->orph_first = c->lpt_last + 1;
+	c->orph_last = c->orph_first + c->orph_lebs - 1;
+	c->main_lebs = c->leb_cnt - UBIFS_SB_LEBS - UBIFS_MST_LEBS;
+	c->main_lebs -= c->log_lebs + c->lpt_lebs + c->orph_lebs;
+	c->main_first = c->leb_cnt - c->main_lebs;
+
+	err = validate_sb(c, sup);
+out:
+	return err;
+}
+
+/**
+ * fixup_leb - fixup/unmap an LEB containing free space.
+ * @c: UBIFS file-system description object
+ * @lnum: the LEB number to fix up
+ * @len: number of used bytes in LEB (starting at offset 0)
+ *
+ * This function reads the contents of the given LEB number @lnum, then fixes
+ * it up, so that empty min. I/O units in the end of LEB are actually erased on
+ * flash (rather than being just all-0xff real data). If the LEB is completely
+ * empty, it is simply unmapped.
+ */
+static int fixup_leb(struct ubifs_info *c, int lnum, int len)
+{
+	int err;
+
+	ubifs_assert(c, len >= 0);
+	ubifs_assert(c, len % c->min_io_size == 0);
+	ubifs_assert(c, len < c->leb_size);
+
+	if (len == 0) {
+		dbg_mnt("unmap empty LEB %d", lnum);
+		return ubifs_leb_unmap(c, lnum);
+	}
+
+	dbg_mnt("fixup LEB %d, data len %d", lnum, len);
+	err = ubifs_leb_read(c, lnum, c->sbuf, 0, len, 1);
+	if (err)
+		return err;
+
+	return ubifs_leb_change(c, lnum, c->sbuf, len);
+}
+
+/**
+ * fixup_free_space - find & remap all LEBs containing free space.
+ * @c: UBIFS file-system description object
+ *
+ * This function walks through all LEBs in the filesystem and fiexes up those
+ * containing free/empty space.
+ */
+static int fixup_free_space(struct ubifs_info *c)
+{
+	int lnum, err = 0;
+	struct ubifs_lprops *lprops;
+
+	ubifs_get_lprops(c);
+
+	/* Fixup LEBs in the master area */
+	for (lnum = UBIFS_MST_LNUM; lnum < UBIFS_LOG_LNUM; lnum++) {
+		err = fixup_leb(c, lnum, c->mst_offs + c->mst_node_alsz);
+		if (err)
+			goto out;
+	}
+
+	/* Unmap unused log LEBs */
+	lnum = ubifs_next_log_lnum(c, c->lhead_lnum);
+	while (lnum != c->ltail_lnum) {
+		err = fixup_leb(c, lnum, 0);
+		if (err)
+			goto out;
+		lnum = ubifs_next_log_lnum(c, lnum);
+	}
+
+	/*
+	 * Fixup the log head which contains the only a CS node at the
+	 * beginning.
+	 */
+	err = fixup_leb(c, c->lhead_lnum,
+			ALIGN(UBIFS_CS_NODE_SZ, c->min_io_size));
+	if (err)
+		goto out;
+
+	/* Fixup LEBs in the LPT area */
+	for (lnum = c->lpt_first; lnum <= c->lpt_last; lnum++) {
+		int free = c->ltab[lnum - c->lpt_first].free;
+
+		if (free > 0) {
+			err = fixup_leb(c, lnum, c->leb_size - free);
+			if (err)
+				goto out;
+		}
+	}
+
+	/* Unmap LEBs in the orphans area */
+	for (lnum = c->orph_first; lnum <= c->orph_last; lnum++) {
+		err = fixup_leb(c, lnum, 0);
+		if (err)
+			goto out;
+	}
+
+	/* Fixup LEBs in the main area */
+	for (lnum = c->main_first; lnum < c->leb_cnt; lnum++) {
+		lprops = ubifs_lpt_lookup(c, lnum);
+		if (IS_ERR(lprops)) {
+			err = PTR_ERR(lprops);
+			goto out;
+		}
+
+		if (lprops->free > 0) {
+			err = fixup_leb(c, lnum, c->leb_size - lprops->free);
+			if (err)
+				goto out;
+		}
+	}
+
+out:
+	ubifs_release_lprops(c);
+	return err;
+}
+
+/**
+ * ubifs_fixup_free_space - find & fix all LEBs with free space.
+ * @c: UBIFS file-system description object
+ *
+ * This function fixes up LEBs containing free space on first mount, if the
+ * appropriate flag was set when the FS was created. Each LEB with one or more
+ * empty min. I/O unit (i.e. free-space-count > 0) is re-written, to make sure
+ * the free space is actually erased. E.g., this is necessary for some NAND
+ * chips, since the free space may have been programmed like real "0xff" data
+ * (generating a non-0xff ECC), causing future writes to the not-really-erased
+ * NAND pages to behave badly. After the space is fixed up, the superblock flag
+ * is cleared, so that this is skipped for all future mounts.
+ */
+int ubifs_fixup_free_space(struct ubifs_info *c)
+{
+	int err;
+	struct ubifs_sb_node *sup = c->sup_node;
+
+	ubifs_assert(c, c->space_fixup);
+	ubifs_assert(c, !c->ro_mount);
+
+	ubifs_msg(c, "start fixing up free space");
+
+	err = fixup_free_space(c);
+	if (err)
+		return err;
+
+	/* Free-space fixup is no longer required */
+	c->space_fixup = 0;
+	sup->flags &= cpu_to_le32(~UBIFS_FLG_SPACE_FIXUP);
+
+	c->superblock_need_write = 1;
+
+	ubifs_msg(c, "free space fixup complete");
+	return err;
+}
+
+int ubifs_enable_encryption(struct ubifs_info *c)
+{
+	int err;
+	struct ubifs_sb_node *sup = c->sup_node;
+
+	if (!IS_ENABLED(CONFIG_FS_ENCRYPTION))
+		return -EOPNOTSUPP;
+
+	if (c->encrypted)
+		return 0;
+
+	if (c->ro_mount || c->ro_media)
+		return -EROFS;
+
+	if (c->fmt_version < 5) {
+		ubifs_err(c, "on-flash format version 5 is needed for encryption");
+		return -EINVAL;
+	}
+
+	sup->flags |= cpu_to_le32(UBIFS_FLG_ENCRYPTION);
+
+	err = ubifs_write_sb_node(c, sup);
+	if (!err)
+		c->encrypted = 1;
+
+	return err;
+}