[PATCH 08/14] hfsplus: implement get and verify block list header functionality

[Vyacheslav Dubeyko <slava@xxxxxxxxxxx>]

From: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
Subject: [PATCH 08/14] hfsplus: implement get and verify block list header functionality

This patch implements functionality of reading of block list's
header from journal log and veryfing of it.

Signed-off-by: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
CC: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
CC: Christoph Hellwig <hch@xxxxxxxxxxxxx>
CC: Hin-Tak Leung <htl10@xxxxxxxxxxxxxxxxxxxxx>
---
 fs/hfsplus/journal.c |  102 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)

diff --git a/fs/hfsplus/journal.c b/fs/hfsplus/journal.c
index 852af82..891be19 100644
--- a/fs/hfsplus/journal.c
+++ b/fs/hfsplus/journal.c
@@ -49,6 +49,18 @@
 #define JHDR_SIZE(jh) \
 	(le32_to_cpu(((struct hfsplus_journal_header *)(jh))->jhdr_size))
 
+#define TR_MAX_BLOCKS(blhdr) \
+	(le16_to_cpu(((struct hfsplus_blhdr *)(blhdr))->max_blocks))
+#define TR_BLOCKS(blhdr) \
+	(le16_to_cpu(((struct hfsplus_blhdr *)(blhdr))->num_blocks))
+#define TR_BYTES(blhdr) \
+	(le32_to_cpu(((struct hfsplus_blhdr *)(blhdr))->bytes_used))
+#define TR_SEQ_NUM(blhdr) \
+	(le32_to_cpu(((struct hfsplus_blhdr *)(blhdr))->binfo[0].block.seq_num))
+#define NEED_CHECK_CSUM(blhdr) \
+	(le32_to_cpu(((struct hfsplus_blhdr *)(blhdr))->flags) & \
+	 HFSPLUS_BLHDR_CHECK_CHECKSUMS)
+
 /*
  * struct hfsplus_blist_desc - descriptor of block list buffer
  * @start_sec: start sector of block list
@@ -295,12 +307,102 @@ static void hfsplus_deinit_block_list_desc(struct hfsplus_blist_desc *desc)
 	kfree(desc->dst_buf);
 }
 
+static struct hfsplus_blhdr *hfsplus_get_blhdr(struct super_block *sb,
+						sector_t start_sector,
+						struct hfsplus_blist_desc *desc)
+{
+	struct hfsplus_blhdr *blhdr;
+	int err;
+
+	hfs_dbg(JREPLAY, "get block list header: start_sector %lu\n",
+		start_sector);
+
+	BUG_ON(!desc->blist_buf);
+
+	if (desc->start_sec == start_sector && desc->cur_sec == start_sector)
+		return &desc->blhdr;
+
+	err = hfsplus_submit_bio(sb, start_sector,
+				 desc->blist_buf, (void **)&blhdr, READA,
+				 &desc->available_bytes);
+	if (err) {
+		pr_err("can't read block list header\n");
+		return NULL;
+	}
+
+	desc->start_sec = start_sector;
+	desc->cur_sec = start_sector;
+	memcpy((void *)&desc->blhdr, (const void *)blhdr, sizeof(*blhdr));
+	desc->binfo = &blhdr->binfo[0];
+
+	return &desc->blhdr;
+}
+
 static inline
 bool hfsplus_journal_empty(struct hfsplus_journal_header *jh)
 {
 	return TR_START(jh) == LAST_TR_END(jh);
 }
 
+static inline
+bool hfsplus_transaction_seq_num_valid(u32 prev_seq_num,
+					struct hfsplus_blhdr *blhdr)
+{
+	if (prev_seq_num != 0) {
+		u32 seq = TR_SEQ_NUM(blhdr);
+
+		if ((seq != 0) && (seq != prev_seq_num) &&
+		    (seq != (prev_seq_num + 1))) {
+			pr_err("transaction seq number %u invalid\n",
+				TR_SEQ_NUM(blhdr));
+			return false;
+		}
+	}
+
+	return true;
+}
+
+static
+int hfsplus_verify_blhdr(u32 prev_seq_num, struct hfsplus_blhdr *blhdr)
+{
+	__le32 blhdr_checksum, cksum;
+
+	if (!hfsplus_transaction_seq_num_valid(prev_seq_num, blhdr))
+		return -EIO;
+
+	if (TR_BLOCKS(blhdr) == 0 || TR_BYTES(blhdr) == 0) {
+		pr_err("corrupted block list header\n");
+		hfs_dbg(JOURNAL, "num_blocks %u, max_blocks %u\n",
+			TR_BLOCKS(blhdr), TR_BYTES(blhdr));
+		return -EIO;
+	}
+
+	if (TR_BLOCKS(blhdr) > TR_MAX_BLOCKS(blhdr)) {
+		pr_err("corrupted block list header\n");
+		hfs_dbg(JOURNAL, "num_blocks %u, max_blocks %u\n",
+			TR_BLOCKS(blhdr), TR_MAX_BLOCKS(blhdr));
+		return -EIO;
+	}
+
+	if (!NEED_CHECK_CSUM(blhdr))
+		return 0; /* don't check checksums */
+
+	blhdr_checksum = blhdr->checksum;
+	blhdr->checksum = 0;
+
+	cksum = HFSPLUS_CALC_CHECKSUM((unsigned char *)blhdr, sizeof(*blhdr));
+	if (le32_to_cpu(cksum) != le32_to_cpu(blhdr_checksum)) {
+		blhdr->checksum = blhdr_checksum;
+		pr_err("corrupted block list header\n");
+		hfs_dbg(JOURNAL, "calculated CRC %#x, blhdr_checksum %#x\n",
+			cksum, be32_to_cpu(blhdr_checksum));
+		return -EIO;
+	}
+
+	blhdr->checksum = blhdr_checksum;
+	return 0;
+}
+
 static int hfsplus_replay_journal(struct super_block *sb);
 
 static
-- 
1.7.9.5



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