- Fix DM integrity crash if "recalculate" used without "internal_hash"

- Fix DM integrity "recalculate" support to prevent recalculating
   checksums if we use internal_hash or journal_hash with a key
   (e.g. HMAC). Use of crypto as a means to prevent malicious
   corruption requires further changes and was never a design goal for
   dm-integrity's primary usecase of detecting accidental corruption.
 
 - Fix a benign dm-crypt copy-and-paste bug introduced as part of a
   fix that was merged for 5.11-rc4.
 
 - Fix DM core's dm_get_device() to avoid filesystem lookup to get
   block device (if possible).
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Merge tag 'for-5.11/dm-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper fixes from Mike Snitzer:

 - Fix DM integrity crash if "recalculate" used without "internal_hash"

 - Fix DM integrity "recalculate" support to prevent recalculating
   checksums if we use internal_hash or journal_hash with a key (e.g.
   HMAC). Use of crypto as a means to prevent malicious corruption
   requires further changes and was never a design goal for
   dm-integrity's primary usecase of detecting accidental corruption.

 - Fix a benign dm-crypt copy-and-paste bug introduced as part of a fix
   that was merged for 5.11-rc4.

 - Fix DM core's dm_get_device() to avoid filesystem lookup to get block
   device (if possible).

* tag 'for-5.11/dm-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm: avoid filesystem lookup in dm_get_dev_t()
  dm crypt: fix copy and paste bug in crypt_alloc_req_aead
  dm integrity: conditionally disable "recalculate" feature
  dm integrity: fix a crash if "recalculate" used without "internal_hash"

Documentation/admin-guide/device-mapper/dm-integrity.rst

@@ -177,14 +177,20 @@ bitmap_flush_interval:number
 	The bitmap flush interval in milliseconds. The metadata buffers
 	are synchronized when this interval expires.
 
+allow_discards
+	Allow block discard requests (a.k.a. TRIM) for the integrity device.
+	Discards are only allowed to devices using internal hash.
+
 fix_padding
 	Use a smaller padding of the tag area that is more
 	space-efficient. If this option is not present, large padding is
 	used - that is for compatibility with older kernels.
 
-allow_discards
-	Allow block discard requests (a.k.a. TRIM) for the integrity device.
-	Discards are only allowed to devices using internal hash.
+legacy_recalculate
+	Allow recalculating of volumes with HMAC keys. This is disabled by
+	default for security reasons - an attacker could modify the volume,
+	set recalc_sector to zero, and the kernel would not detect the
+	modification.
 
 The journal mode (D/J), buffer_sectors, journal_watermark, commit_time and
 allow_discards can be changed when reloading the target (load an inactive

drivers/md/dm-crypt.c

@@ -1481,9 +1481,9 @@ static int crypt_alloc_req_skcipher(struct crypt_config *cc,
 static int crypt_alloc_req_aead(struct crypt_config *cc,
 				 struct convert_context *ctx)
 {
-	if (!ctx->r.req) {
-		ctx->r.req = mempool_alloc(&cc->req_pool, in_interrupt() ? GFP_ATOMIC : GFP_NOIO);
-		if (!ctx->r.req)
+	if (!ctx->r.req_aead) {
+		ctx->r.req_aead = mempool_alloc(&cc->req_pool, in_interrupt() ? GFP_ATOMIC : GFP_NOIO);
+		if (!ctx->r.req_aead)
 			return -ENOMEM;
 	}
 

drivers/md/dm-integrity.c

@@ -257,8 +257,9 @@ struct dm_integrity_c {
 	bool journal_uptodate;
 	bool just_formatted;
 	bool recalculate_flag;
-	bool fix_padding;
 	bool discard;
+	bool fix_padding;
+	bool legacy_recalculate;
 
 	struct alg_spec internal_hash_alg;
 	struct alg_spec journal_crypt_alg;
@@ -386,6 +387,14 @@ static int dm_integrity_failed(struct dm_integrity_c *ic)
 	return READ_ONCE(ic->failed);
 }
 
+static bool dm_integrity_disable_recalculate(struct dm_integrity_c *ic)
+{
+	if ((ic->internal_hash_alg.key || ic->journal_mac_alg.key) &&
+	    !ic->legacy_recalculate)
+		return true;
+	return false;
+}
+
 static commit_id_t dm_integrity_commit_id(struct dm_integrity_c *ic, unsigned i,
 					  unsigned j, unsigned char seq)
 {
@@ -3140,6 +3149,7 @@ static void dm_integrity_status(struct dm_target *ti, status_type_t type,
 		arg_count += !!ic->journal_crypt_alg.alg_string;
 		arg_count += !!ic->journal_mac_alg.alg_string;
 		arg_count += (ic->sb->flags & cpu_to_le32(SB_FLAG_FIXED_PADDING)) != 0;
+		arg_count += ic->legacy_recalculate;
 		DMEMIT("%s %llu %u %c %u", ic->dev->name, ic->start,
 		       ic->tag_size, ic->mode, arg_count);
 		if (ic->meta_dev)
@@ -3163,6 +3173,8 @@ static void dm_integrity_status(struct dm_target *ti, status_type_t type,
 		}
 		if ((ic->sb->flags & cpu_to_le32(SB_FLAG_FIXED_PADDING)) != 0)
 			DMEMIT(" fix_padding");
+		if (ic->legacy_recalculate)
+			DMEMIT(" legacy_recalculate");
 
 #define EMIT_ALG(a, n)							\
 		do {							\
@@ -3792,7 +3804,7 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	unsigned extra_args;
 	struct dm_arg_set as;
 	static const struct dm_arg _args[] = {
-		{0, 15, "Invalid number of feature args"},
+		{0, 16, "Invalid number of feature args"},
 	};
 	unsigned journal_sectors, interleave_sectors, buffer_sectors, journal_watermark, sync_msec;
 	bool should_write_sb;
@@ -3940,6 +3952,8 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 			ic->discard = true;
 		} else if (!strcmp(opt_string, "fix_padding")) {
 			ic->fix_padding = true;
+		} else if (!strcmp(opt_string, "legacy_recalculate")) {
+			ic->legacy_recalculate = true;
 		} else {
 			r = -EINVAL;
 			ti->error = "Invalid argument";
@@ -4235,6 +4249,20 @@ try_smaller_buffer:
 			r = -ENOMEM;
 			goto bad;
 		}
+	} else {
+		if (ic->sb->flags & cpu_to_le32(SB_FLAG_RECALCULATING)) {
+			ti->error = "Recalculate can only be specified with internal_hash";
+			r = -EINVAL;
+			goto bad;
+		}
+	}
+
+	if (ic->sb->flags & cpu_to_le32(SB_FLAG_RECALCULATING) &&
+	    le64_to_cpu(ic->sb->recalc_sector) < ic->provided_data_sectors &&
+	    dm_integrity_disable_recalculate(ic)) {
+		ti->error = "Recalculating with HMAC is disabled for security reasons - if you really need it, use the argument \"legacy_recalculate\"";
+		r = -EOPNOTSUPP;
+		goto bad;
 	}
 
 	ic->bufio = dm_bufio_client_create(ic->meta_dev ? ic->meta_dev->bdev : ic->dev->bdev,

drivers/md/dm-table.c

@@ -363,14 +363,23 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
 {
 	int r;
 	dev_t dev;
+	unsigned int major, minor;
+	char dummy;
 	struct dm_dev_internal *dd;
 	struct dm_table *t = ti->table;
 
 	BUG_ON(!t);
 
-	dev = dm_get_dev_t(path);
-	if (!dev)
-		return -ENODEV;
+	if (sscanf(path, "%u:%u%c", &major, &minor, &dummy) == 2) {
+		/* Extract the major/minor numbers */
+		dev = MKDEV(major, minor);
+		if (MAJOR(dev) != major || MINOR(dev) != minor)
+			return -EOVERFLOW;
+	} else {
+		dev = dm_get_dev_t(path);
+		if (!dev)
+			return -ENODEV;
+	}
 
 	dd = find_device(&t->devices, dev);
 	if (!dd) {