Merge tag 'upstream-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/ubifs

Pull UBIFS updates from Richard Weinberger:

 - Support for zstd compression

 - Support for offline signed filesystems

 - Various fixes for regressions

* tag 'upstream-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/ubifs:
  ubifs: Don't leak orphans on memory during commit
  ubifs: Check link count of inodes when killing orphans.
  ubifs: Add support for zstd compression.
  ubifs: support offline signed images
  ubifs: remove unnecessary check in ubifs_log_start_commit
  ubifs: Fix typo of output in get_cs_sqnum
  ubifs: Simplify redundant code
  ubifs: Correctly use tnc_next() in search_dh_cookie()

12 files changed, 338 insertions, 92 deletions

diff --git a/fs/ubifs/Kconfig b/fs/ubifs/Kconfig
index 06c35c64162b..69932bcfa920 100644
--- a/fs/ubifs/Kconfig
+++ b/fs/ubifs/Kconfig
@@ -6,8 +6,10 @@ config UBIFS_FS
 	select CRYPTO if UBIFS_FS_ADVANCED_COMPR
 	select CRYPTO if UBIFS_FS_LZO
 	select CRYPTO if UBIFS_FS_ZLIB
+	select CRYPTO if UBIFS_FS_ZSTD
 	select CRYPTO_LZO if UBIFS_FS_LZO
 	select CRYPTO_DEFLATE if UBIFS_FS_ZLIB
+	select CRYPTO_ZSTD if UBIFS_FS_ZSTD
 	select CRYPTO_HASH_INFO
 	select UBIFS_FS_XATTR if FS_ENCRYPTION
 	depends on MTD_UBI
@@ -38,6 +40,14 @@ config UBIFS_FS_ZLIB
 	help
 	  Zlib compresses better than LZO but it is slower. Say 'Y' if unsure.
 
+config UBIFS_FS_ZSTD
+	bool "ZSTD compression support" if UBIFS_FS_ADVANCED_COMPR
+	depends on UBIFS_FS
+	default y
+	help
+	  ZSTD compresses is a big win in speed over Zlib and
+	  in compression ratio over LZO. Say 'Y' if unsure.
+
 config UBIFS_ATIME_SUPPORT
 	bool "Access time support"
 	default n
@@ -77,8 +87,9 @@ config UBIFS_FS_SECURITY
 
 config UBIFS_FS_AUTHENTICATION
 	bool "UBIFS authentication support"
-	depends on KEYS
+	select KEYS
 	select CRYPTO_HMAC
+	select SYSTEM_DATA_VERIFICATION
 	help
 	  Enable authentication support for UBIFS. This feature offers protection
 	  against offline changes for both data and metadata of the filesystem.
diff --git a/fs/ubifs/auth.c b/fs/ubifs/auth.c
index 60f43b93d06e..d9af2de9084a 100644
--- a/fs/ubifs/auth.c
+++ b/fs/ubifs/auth.c
@@ -10,10 +10,12 @@
  */
 
 #include <linux/crypto.h>
+#include <linux/verification.h>
 #include <crypto/hash.h>
 #include <crypto/sha.h>
 #include <crypto/algapi.h>
 #include <keys/user-type.h>
+#include <keys/asymmetric-type.h>
 
 #include "ubifs.h"
 
@@ -199,6 +201,77 @@ int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node,
 }
 
 /**
+ * ubifs_sb_verify_signature - verify the signature of a superblock
+ * @c: UBIFS file-system description object
+ * @sup: The superblock node
+ *
+ * To support offline signed images the superblock can be signed with a
+ * PKCS#7 signature. The signature is placed directly behind the superblock
+ * node in an ubifs_sig_node.
+ *
+ * Returns 0 when the signature can be successfully verified or a negative
+ * error code if not.
+ */
+int ubifs_sb_verify_signature(struct ubifs_info *c,
+			      const struct ubifs_sb_node *sup)
+{
+	int err;
+	struct ubifs_scan_leb *sleb;
+	struct ubifs_scan_node *snod;
+	const struct ubifs_sig_node *signode;
+
+	sleb = ubifs_scan(c, UBIFS_SB_LNUM, UBIFS_SB_NODE_SZ, c->sbuf, 0);
+	if (IS_ERR(sleb)) {
+		err = PTR_ERR(sleb);
+		return err;
+	}
+
+	if (sleb->nodes_cnt == 0) {
+		ubifs_err(c, "Unable to find signature node");
+		err = -EINVAL;
+		goto out_destroy;
+	}
+
+	snod = list_first_entry(&sleb->nodes, struct ubifs_scan_node, list);
+
+	if (snod->type != UBIFS_SIG_NODE) {
+		ubifs_err(c, "Signature node is of wrong type");
+		err = -EINVAL;
+		goto out_destroy;
+	}
+
+	signode = snod->node;
+
+	if (le32_to_cpu(signode->len) > snod->len + sizeof(struct ubifs_sig_node)) {
+		ubifs_err(c, "invalid signature len %d", le32_to_cpu(signode->len));
+		err = -EINVAL;
+		goto out_destroy;
+	}
+
+	if (le32_to_cpu(signode->type) != UBIFS_SIGNATURE_TYPE_PKCS7) {
+		ubifs_err(c, "Signature type %d is not supported\n",
+			  le32_to_cpu(signode->type));
+		err = -EINVAL;
+		goto out_destroy;
+	}
+
+	err = verify_pkcs7_signature(sup, sizeof(struct ubifs_sb_node),
+				     signode->sig, le32_to_cpu(signode->len),
+				     NULL, VERIFYING_UNSPECIFIED_SIGNATURE,
+				     NULL, NULL);
+
+	if (err)
+		ubifs_err(c, "Failed to verify signature");
+	else
+		ubifs_msg(c, "Successfully verified super block signature");
+
+out_destroy:
+	ubifs_scan_destroy(sleb);
+
+	return err;
+}
+
+/**
  * ubifs_init_authentication - initialize UBIFS authentication support
  * @c: UBIFS file-system description object
  *
@@ -478,3 +551,16 @@ int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac)
 		return err;
 	return 0;
 }
+
+/*
+ * ubifs_hmac_zero - test if a HMAC is zero
+ * @c: UBIFS file-system description object
+ * @hmac: the HMAC to test
+ *
+ * This function tests if a HMAC is zero and returns true if it is
+ * and false otherwise.
+ */
+bool ubifs_hmac_zero(struct ubifs_info *c, const u8 *hmac)
+{
+	return !memchr_inv(hmac, 0, c->hmac_desc_len);
+}
diff --git a/fs/ubifs/compress.c b/fs/ubifs/compress.c
index 99c53ad11e93..3a92e6af69b2 100644
--- a/fs/ubifs/compress.c
+++ b/fs/ubifs/compress.c
@@ -59,6 +59,24 @@ static struct ubifs_compressor zlib_compr = {
 };
 #endif
 
+#ifdef CONFIG_UBIFS_FS_ZSTD
+static DEFINE_MUTEX(zstd_enc_mutex);
+static DEFINE_MUTEX(zstd_dec_mutex);
+
+static struct ubifs_compressor zstd_compr = {
+	.compr_type = UBIFS_COMPR_ZSTD,
+	.comp_mutex = &zstd_enc_mutex,
+	.decomp_mutex = &zstd_dec_mutex,
+	.name = "zstd",
+	.capi_name = "zstd",
+};
+#else
+static struct ubifs_compressor zstd_compr = {
+	.compr_type = UBIFS_COMPR_ZSTD,
+	.name = "zstd",
+};
+#endif
+
 /* All UBIFS compressors */
 struct ubifs_compressor *ubifs_compressors[UBIFS_COMPR_TYPES_CNT];
 
@@ -216,13 +234,19 @@ int __init ubifs_compressors_init(void)
 	if (err)
 		return err;
 
-	err = compr_init(&zlib_compr);
+	err = compr_init(&zstd_compr);
 	if (err)
 		goto out_lzo;
 
+	err = compr_init(&zlib_compr);
+	if (err)
+		goto out_zstd;
+
 	ubifs_compressors[UBIFS_COMPR_NONE] = &none_compr;
 	return 0;
 
+out_zstd:
+	compr_exit(&zstd_compr);
 out_lzo:
 	compr_exit(&lzo_compr);
 	return err;
@@ -235,4 +259,5 @@ void ubifs_compressors_exit(void)
 {
 	compr_exit(&lzo_compr);
 	compr_exit(&zlib_compr);
+	compr_exit(&zstd_compr);
 }
diff --git a/fs/ubifs/log.c b/fs/ubifs/log.c
index cd85d7d4c515..b6ac9c4281ef 100644
--- a/fs/ubifs/log.c
+++ b/fs/ubifs/log.c
@@ -438,10 +438,7 @@ int ubifs_log_start_commit(struct ubifs_info *c, int *ltail_lnum)
 	*ltail_lnum = c->lhead_lnum;
 
 	c->lhead_offs += len;
-	if (c->lhead_offs == c->leb_size) {
-		c->lhead_lnum = ubifs_next_log_lnum(c, c->lhead_lnum);
-		c->lhead_offs = 0;
-	}
+	ubifs_assert(c, c->lhead_offs < c->leb_size);
 
 	remove_buds(c);
 
diff --git a/fs/ubifs/master.c b/fs/ubifs/master.c
index b42a768709c0..52a85c01397e 100644
--- a/fs/ubifs/master.c
+++ b/fs/ubifs/master.c
@@ -48,6 +48,39 @@ int ubifs_compare_master_node(struct ubifs_info *c, void *m1, void *m2)
 	return 0;
 }
 
+/* mst_node_check_hash - Check hash of a master node
+ * @c: UBIFS file-system description object
+ * @mst: The master node
+ * @expected: The expected hash of the master node
+ *
+ * This checks the hash of a master node against a given expected hash.
+ * Note that we have two master nodes on a UBIFS image which have different
+ * sequence numbers and consequently different CRCs. To be able to match
+ * both master nodes we exclude the common node header containing the sequence
+ * number and CRC from the hash.
+ *
+ * Returns 0 if the hashes are equal, a negative error code otherwise.
+ */
+static int mst_node_check_hash(const struct ubifs_info *c,
+			       const struct ubifs_mst_node *mst,
+			       const u8 *expected)
+{
+	u8 calc[UBIFS_MAX_HASH_LEN];
+	const void *node = mst;
+
+	SHASH_DESC_ON_STACK(shash, c->hash_tfm);
+
+	shash->tfm = c->hash_tfm;
+
+	crypto_shash_digest(shash, node + sizeof(struct ubifs_ch),
+			    UBIFS_MST_NODE_SZ - sizeof(struct ubifs_ch), calc);
+
+	if (ubifs_check_hash(c, expected, calc))
+		return -EPERM;
+
+	return 0;
+}
+
 /**
  * scan_for_master - search the valid master node.
  * @c: UBIFS file-system description object
@@ -102,14 +135,22 @@ static int scan_for_master(struct ubifs_info *c)
 	if (!ubifs_authenticated(c))
 		return 0;
 
-	err = ubifs_node_verify_hmac(c, c->mst_node,
-				     sizeof(struct ubifs_mst_node),
-				     offsetof(struct ubifs_mst_node, hmac));
-	if (err) {
-		ubifs_err(c, "Failed to verify master node HMAC");
-		return -EPERM;
+	if (ubifs_hmac_zero(c, c->mst_node->hmac)) {
+		err = mst_node_check_hash(c, c->mst_node,
+					  c->sup_node->hash_mst);
+		if (err)
+			ubifs_err(c, "Failed to verify master node hash");
+	} else {
+		err = ubifs_node_verify_hmac(c, c->mst_node,
+					sizeof(struct ubifs_mst_node),
+					offsetof(struct ubifs_mst_node, hmac));
+		if (err)
+			ubifs_err(c, "Failed to verify master node HMAC");
 	}
 
+	if (err)
+		return -EPERM;
+
 	return 0;
 
 out:
diff --git a/fs/ubifs/orphan.c b/fs/ubifs/orphan.c
index cb72688032cd..b52624e28fa1 100644
--- a/fs/ubifs/orphan.c
+++ b/fs/ubifs/orphan.c
@@ -126,25 +126,11 @@ static void __orphan_drop(struct ubifs_info *c, struct ubifs_orphan *o)
 	kfree(o);
 }
 
-static void orphan_delete(struct ubifs_info *c, ino_t inum)
+static void orphan_delete(struct ubifs_info *c, struct ubifs_orphan *orph)
 {
-	struct ubifs_orphan *orph, *child_orph, *tmp_o;
-
-	spin_lock(&c->orphan_lock);
-
-	orph = lookup_orphan(c, inum);
-	if (!orph) {
-		spin_unlock(&c->orphan_lock);
-		ubifs_err(c, "missing orphan ino %lu", (unsigned long)inum);
-		dump_stack();
-
-		return;
-	}
-
 	if (orph->del) {
 		spin_unlock(&c->orphan_lock);
-		dbg_gen("deleted twice ino %lu",
-			(unsigned long)inum);
+		dbg_gen("deleted twice ino %lu", orph->inum);
 		return;
 	}
 
@@ -153,19 +139,11 @@ static void orphan_delete(struct ubifs_info *c, ino_t inum)
 		orph->dnext = c->orph_dnext;
 		c->orph_dnext = orph;
 		spin_unlock(&c->orphan_lock);
-		dbg_gen("delete later ino %lu",
-			(unsigned long)inum);
+		dbg_gen("delete later ino %lu", orph->inum);
 		return;
 	}
 
-	list_for_each_entry_safe(child_orph, tmp_o, &orph->child_list, child_list) {
-		list_del(&child_orph->child_list);
-		__orphan_drop(c, child_orph);
-	}
-
 	__orphan_drop(c, orph);
-
-	spin_unlock(&c->orphan_lock);
 }
 
 /**
@@ -223,7 +201,27 @@ int ubifs_add_orphan(struct ubifs_info *c, ino_t inum)
  */
 void ubifs_delete_orphan(struct ubifs_info *c, ino_t inum)
 {
-	orphan_delete(c, inum);
+	struct ubifs_orphan *orph, *child_orph, *tmp_o;
+
+	spin_lock(&c->orphan_lock);
+
+	orph = lookup_orphan(c, inum);
+	if (!orph) {
+		spin_unlock(&c->orphan_lock);
+		ubifs_err(c, "missing orphan ino %lu", (unsigned long)inum);
+		dump_stack();
+
+		return;
+	}
+
+	list_for_each_entry_safe(child_orph, tmp_o, &orph->child_list, child_list) {
+		list_del(&child_orph->child_list);
+		orphan_delete(c, child_orph);
+	}
+	
+	orphan_delete(c, orph);
+
+	spin_unlock(&c->orphan_lock);
 }
 
 /**
@@ -630,6 +628,7 @@ static int do_kill_orphans(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
 {
 	struct ubifs_scan_node *snod;
 	struct ubifs_orph_node *orph;
+	struct ubifs_ino_node *ino = NULL;
 	unsigned long long cmt_no;
 	ino_t inum;
 	int i, n, err, first = 1;
@@ -676,23 +675,40 @@ static int do_kill_orphans(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
 		if (first)
 			first = 0;
 
+		ino = kmalloc(UBIFS_MAX_INO_NODE_SZ, GFP_NOFS);
+		if (!ino)
+			return -ENOMEM;
+
 		n = (le32_to_cpu(orph->ch.len) - UBIFS_ORPH_NODE_SZ) >> 3;
 		for (i = 0; i < n; i++) {
 			union ubifs_key key1, key2;
 
 			inum = le64_to_cpu(orph->inos[i]);
-			dbg_rcvry("deleting orphaned inode %lu",
-				  (unsigned long)inum);
-
-			lowest_ino_key(c, &key1, inum);
-			highest_ino_key(c, &key2, inum);
 
-			err = ubifs_tnc_remove_range(c, &key1, &key2);
+			ino_key_init(c, &key1, inum);
+			err = ubifs_tnc_lookup(c, &key1, ino);
 			if (err)
-				return err;
+				goto out_free;
+
+			/*
+			 * Check whether an inode can really get deleted.
+			 * linkat() with O_TMPFILE allows rebirth of an inode.
+			 */
+			if (ino->nlink == 0) {
+				dbg_rcvry("deleting orphaned inode %lu",
+					  (unsigned long)inum);
+
+				lowest_ino_key(c, &key1, inum);
+				highest_ino_key(c, &key2, inum);
+
+				err = ubifs_tnc_remove_range(c, &key1, &key2);
+				if (err)
+					goto out_ro;
+			}
+
 			err = insert_dead_orphan(c, inum);
 			if (err)
-				return err;
+				goto out_free;
 		}
 
 		*last_cmt_no = cmt_no;
@@ -704,7 +720,15 @@ static int do_kill_orphans(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
 			*last_flagged = 0;
 	}
 
-	return 0;
+	err = 0;
+out_free:
+	kfree(ino);
+	return err;
+
+out_ro:
+	ubifs_ro_mode(c, err);
+	kfree(ino);
+	return err;
 }
 
 /**
diff --git a/fs/ubifs/recovery.c b/fs/ubifs/recovery.c
index 3fc589881825..f116f7b3f9e5 100644
--- a/fs/ubifs/recovery.c
+++ b/fs/ubifs/recovery.c
@@ -818,7 +818,7 @@ static int get_cs_sqnum(struct ubifs_info *c, int lnum, int offs,
 		goto out_err;
 	}
 	if (cs_node->ch.node_type != UBIFS_CS_NODE) {
-		ubifs_err(c, "Node a CS node, type is %d", cs_node->ch.node_type);
+		ubifs_err(c, "Not a CS node, type is %d", cs_node->ch.node_type);
 		goto out_err;
 	}
 	if (le64_to_cpu(cs_node->cmt_no) != c->cmt_no) {
diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
index 12c2afdb5804..a551eb3e9b89 100644
--- a/fs/ubifs/sb.c
+++ b/fs/ubifs/sb.c
@@ -578,17 +578,26 @@ static int authenticate_sb_node(struct ubifs_info *c,
 		return -EINVAL;
 	}
 
-	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;
+	/*
+	 * 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));
 	}
 
-	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);
 
@@ -744,21 +753,16 @@ int ubifs_read_superblock(struct ubifs_info *c)
 	}
 
 	/* Automatically increase file system size to the maximum size */
-	c->old_leb_cnt = c->leb_cnt;
 	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);
-		if (c->ro_mount)
-			dbg_mnt("Auto resizing (ro) from %d LEBs to %d LEBs",
-				c->old_leb_cnt,	c->leb_cnt);
-		else {
-			dbg_mnt("Auto resizing (sb) from %d LEBs to %d LEBs",
-				c->old_leb_cnt, c->leb_cnt);
-			sup->leb_cnt = cpu_to_le32(c->leb_cnt);
-			err = ubifs_write_sb_node(c, sup);
-			if (err)
-				goto out;
-			c->old_leb_cnt = c->leb_cnt;
-		}
+		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;
@@ -916,9 +920,7 @@ int ubifs_fixup_free_space(struct ubifs_info *c)
 	c->space_fixup = 0;
 	sup->flags &= cpu_to_le32(~UBIFS_FLG_SPACE_FIXUP);
 
-	err = ubifs_write_sb_node(c, sup);
-	if (err)
-		return err;
+	c->superblock_need_write = 1;
 
 	ubifs_msg(c, "free space fixup complete");
 	return err;
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index fd1977b568f0..2c0803b0ac3a 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -566,6 +566,8 @@ static int init_constants_early(struct ubifs_info *c)
 	c->ranges[UBIFS_AUTH_NODE].min_len = UBIFS_AUTH_NODE_SZ;
 	c->ranges[UBIFS_AUTH_NODE].max_len = UBIFS_AUTH_NODE_SZ +
 				UBIFS_MAX_HMAC_LEN;
+	c->ranges[UBIFS_SIG_NODE].min_len = UBIFS_SIG_NODE_SZ;
+	c->ranges[UBIFS_SIG_NODE].max_len = c->leb_size - UBIFS_SB_NODE_SZ;
 
 	c->ranges[UBIFS_INO_NODE].min_len  = UBIFS_INO_NODE_SZ;
 	c->ranges[UBIFS_INO_NODE].max_len  = UBIFS_MAX_INO_NODE_SZ;
@@ -1043,6 +1045,8 @@ static int ubifs_parse_options(struct ubifs_info *c, char *options,
 				c->mount_opts.compr_type = UBIFS_COMPR_LZO;
 			else if (!strcmp(name, "zlib"))
 				c->mount_opts.compr_type = UBIFS_COMPR_ZLIB;
+			else if (!strcmp(name, "zstd"))
+				c->mount_opts.compr_type = UBIFS_COMPR_ZSTD;
 			else {
 				ubifs_err(c, "unknown compressor \"%s\"", name); //FIXME: is c ready?
 				kfree(name);
@@ -1296,8 +1300,7 @@ static int mount_ubifs(struct ubifs_info *c)
 	if (err)
 		goto out_free;
 
-	sz = ALIGN(c->max_idx_node_sz, c->min_io_size);
-	sz = ALIGN(sz + c->max_idx_node_sz, c->min_io_size);
+	sz = ALIGN(c->max_idx_node_sz, c->min_io_size) * 2;
 	c->cbuf = kmalloc(sz, GFP_NOFS);
 	if (!c->cbuf) {
 		err = -ENOMEM;
@@ -1360,6 +1363,26 @@ static int mount_ubifs(struct ubifs_info *c)
 			goto out_lpt;
 	}
 
+	/*
+	 * Handle offline signed images: Now that the master node is
+	 * written and its validation no longer depends on the hash
+	 * in the superblock, we can update the offline signed
+	 * superblock with a HMAC version,
+	 */
+	if (ubifs_authenticated(c) && ubifs_hmac_zero(c, c->sup_node->hmac)) {
+		err = ubifs_hmac_wkm(c, c->sup_node->hmac_wkm);
+		if (err)
+			goto out_lpt;
+		c->superblock_need_write = 1;
+	}
+
+	if (!c->ro_mount && c->superblock_need_write) {
+		err = ubifs_write_sb_node(c, c->sup_node);
+		if (err)
+			goto out_lpt;
+		c->superblock_need_write = 0;
+	}
+
 	err = dbg_check_idx_size(c, c->bi.old_idx_sz);
 	if (err)
 		goto out_lpt;
@@ -1642,15 +1665,6 @@ static int ubifs_remount_rw(struct ubifs_info *c)
 	if (err)
 		goto out;
 
-	if (c->old_leb_cnt != c->leb_cnt) {
-		struct ubifs_sb_node *sup = c->sup_node;
-
-		sup->leb_cnt = cpu_to_le32(c->leb_cnt);
-		err = ubifs_write_sb_node(c, sup);
-		if (err)
-			goto out;
-	}
-
 	if (c->need_recovery) {
 		ubifs_msg(c, "completing deferred recovery");
 		err = ubifs_write_rcvrd_mst_node(c);
@@ -1682,6 +1696,16 @@ static int ubifs_remount_rw(struct ubifs_info *c)
 			goto out;
 	}
 
+	if (c->superblock_need_write) {
+		struct ubifs_sb_node *sup = c->sup_node;
+
+		err = ubifs_write_sb_node(c, sup);
+		if (err)
+			goto out;
+
+		c->superblock_need_write = 0;
+	}
+
 	c->ileb_buf = vmalloc(c->leb_size);
 	if (!c->ileb_buf) {
 		err = -ENOMEM;
diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
index f5a823cb0e43..e8e7b0e9532e 100644
--- a/fs/ubifs/tnc.c
+++ b/fs/ubifs/tnc.c
@@ -1158,8 +1158,8 @@ static struct ubifs_znode *dirty_cow_bottom_up(struct ubifs_info *c,
  *   o exact match, i.e. the found zero-level znode contains key @key, then %1
  *     is returned and slot number of the matched branch is stored in @n;
  *   o not exact match, which means that zero-level znode does not contain
- *     @key, then %0 is returned and slot number of the closest branch is stored
- *     in @n;
+ *     @key, then %0 is returned and slot number of the closest branch or %-1
+ *     is stored in @n; In this case calling tnc_next() is mandatory.
  *   o @key is so small that it is even less than the lowest key of the
  *     leftmost zero-level node, then %0 is returned and %0 is stored in @n.
  *
@@ -1882,13 +1882,19 @@ int ubifs_tnc_lookup_nm(struct ubifs_info *c, const union ubifs_key *key,
 
 static int search_dh_cookie(struct ubifs_info *c, const union ubifs_key *key,
 			    struct ubifs_dent_node *dent, uint32_t cookie,
-			    struct ubifs_znode **zn, int *n)
+			    struct ubifs_znode **zn, int *n, int exact)
 {
 	int err;
 	struct ubifs_znode *znode = *zn;
 	struct ubifs_zbranch *zbr;
 	union ubifs_key *dkey;
 
+	if (!exact) {
+		err = tnc_next(c, &znode, n);
+		if (err)
+			return err;
+	}
+
 	for (;;) {
 		zbr = &znode->zbranch[*n];
 		dkey = &zbr->key;
@@ -1930,7 +1936,7 @@ static int do_lookup_dh(struct ubifs_info *c, const union ubifs_key *key,
 	if (unlikely(err < 0))
 		goto out_unlock;
 
-	err = search_dh_cookie(c, key, dent, cookie, &znode, &n);
+	err = search_dh_cookie(c, key, dent, cookie, &znode, &n, err);
 
 out_unlock:
 	mutex_unlock(&c->tnc_mutex);
@@ -2723,7 +2729,7 @@ int ubifs_tnc_remove_dh(struct ubifs_info *c, const union ubifs_key *key,
 		if (unlikely(err < 0))
 			goto out_free;
 
-		err = search_dh_cookie(c, key, dent, cookie, &znode, &n);
+		err = search_dh_cookie(c, key, dent, cookie, &znode, &n, err);
 		if (err)
 			goto out_free;
 	}
diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h
index 86f0f2be116c..3c9792cbb6ff 100644
--- a/fs/ubifs/ubifs-media.h
+++ b/fs/ubifs/ubifs-media.h
@@ -275,6 +275,8 @@ enum {
 #define UBIFS_CS_NODE_SZ   sizeof(struct ubifs_cs_node)
 #define UBIFS_ORPH_NODE_SZ sizeof(struct ubifs_orph_node)
 #define UBIFS_AUTH_NODE_SZ sizeof(struct ubifs_auth_node)
+#define UBIFS_SIG_NODE_SZ  sizeof(struct ubifs_sig_node)
+
 /* Extended attribute entry nodes are identical to directory entry nodes */
 #define UBIFS_XENT_NODE_SZ UBIFS_DENT_NODE_SZ
 /* Only this does not have to be multiple of 8 bytes */
@@ -301,6 +303,8 @@ enum {
  */
 #define UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT "c"
 
+/* Type field in ubifs_sig_node */
+#define UBIFS_SIGNATURE_TYPE_PKCS7	1
 
 /*
  * On-flash inode flags.
@@ -336,12 +340,14 @@ enum {
  * UBIFS_COMPR_NONE: no compression
  * UBIFS_COMPR_LZO: LZO compression
  * UBIFS_COMPR_ZLIB: ZLIB compression
+ * UBIFS_COMPR_ZSTD: ZSTD compression
  * UBIFS_COMPR_TYPES_CNT: count of supported compression types
  */
 enum {
 	UBIFS_COMPR_NONE,
 	UBIFS_COMPR_LZO,
 	UBIFS_COMPR_ZLIB,
+	UBIFS_COMPR_ZSTD,
 	UBIFS_COMPR_TYPES_CNT,
 };
 
@@ -361,6 +367,7 @@ enum {
  * UBIFS_CS_NODE: commit start node
  * UBIFS_ORPH_NODE: orphan node
  * UBIFS_AUTH_NODE: authentication node
+ * UBIFS_SIG_NODE: signature node
  * UBIFS_NODE_TYPES_CNT: count of supported node types
  *
  * Note, we index arrays by these numbers, so keep them low and contiguous.
@@ -381,6 +388,7 @@ enum {
 	UBIFS_CS_NODE,
 	UBIFS_ORPH_NODE,
 	UBIFS_AUTH_NODE,
+	UBIFS_SIG_NODE,
 	UBIFS_NODE_TYPES_CNT,
 };
 
@@ -638,6 +646,8 @@ struct ubifs_pad_node {
  * @hmac_wkm: HMAC of a well known message (the string "UBIFS") as a convenience
  *            to the user to check if the correct key is passed.
  * @hash_algo: The hash algo used for this filesystem (one of enum hash_algo)
+ * @hash_mst: hash of the master node, only valid for signed images in which the
+ *            master node does not contain a hmac
  */
 struct ubifs_sb_node {
 	struct ubifs_ch ch;
@@ -668,7 +678,8 @@ struct ubifs_sb_node {
 	__u8 hmac[UBIFS_MAX_HMAC_LEN];
 	__u8 hmac_wkm[UBIFS_MAX_HMAC_LEN];
 	__le16 hash_algo;
-	__u8 padding2[3838];
+	__u8 hash_mst[UBIFS_MAX_HASH_LEN];
+	__u8 padding2[3774];
 } __packed;
 
 /**
@@ -771,6 +782,23 @@ struct ubifs_auth_node {
 } __packed;
 
 /**
+ * struct ubifs_sig_node - node for signing other nodes
+ * @ch: common header
+ * @type: type of the signature, currently only UBIFS_SIGNATURE_TYPE_PKCS7
+ * supported
+ * @len: The length of the signature data
+ * @padding: reserved for future, zeroes
+ * @sig: The signature data
+ */
+struct ubifs_sig_node {
+	struct ubifs_ch ch;
+	__le32 type;
+	__le32 len;
+	__u8 padding[32];
+	__u8 sig[];
+} __packed;
+
+/**
  * struct ubifs_branch - key/reference/length branch
  * @lnum: LEB number of the target node
  * @offs: offset within @lnum
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 745b23e5b406..c55f212dcb75 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1104,7 +1104,6 @@ struct ubifs_debug_info;
  *                used to store indexing nodes (@leb_size - @max_idx_node_sz)
  * @leb_cnt: count of logical eraseblocks
  * @max_leb_cnt: maximum count of logical eraseblocks
- * @old_leb_cnt: count of logical eraseblocks before re-size
  * @ro_media: the underlying UBI volume is read-only
  * @ro_mount: the file-system was mounted as read-only
  * @ro_error: UBIFS switched to R/O mode because an error happened
@@ -1295,6 +1294,7 @@ struct ubifs_info {
 	unsigned int rw_incompat:1;
 	unsigned int assert_action:2;
 	unsigned int authenticated:1;
+	unsigned int superblock_need_write:1;
 
 	struct mutex tnc_mutex;
 	struct ubifs_zbranch zroot;
@@ -1352,7 +1352,6 @@ struct ubifs_info {
 	int idx_leb_size;
 	int leb_cnt;
 	int max_leb_cnt;
-	int old_leb_cnt;
 	unsigned int ro_media:1;
 	unsigned int ro_mount:1;
 	unsigned int ro_error:1;
@@ -1680,6 +1679,9 @@ static inline int ubifs_auth_node_sz(const struct ubifs_info *c)
 	else
 		return 0;
 }
+int ubifs_sb_verify_signature(struct ubifs_info *c,
+			      const struct ubifs_sb_node *sup);
+bool ubifs_hmac_zero(struct ubifs_info *c, const u8 *hmac);
 
 int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac);