1 files changed, 65 insertions, 8 deletions

diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index c8b89b4f94e0..2064e6473d30 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -13,6 +13,7 @@
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
 #include <linux/random.h>
+#include <linux/log2.h>
 #include <linux/crc32.h>
 #include "nilfs.h"
 #include "segment.h"
@@ -193,6 +194,34 @@ static int nilfs_store_log_cursor(struct the_nilfs *nilfs,
 }
 
 /**
+ * nilfs_get_blocksize - get block size from raw superblock data
+ * @sb: super block instance
+ * @sbp: superblock raw data buffer
+ * @blocksize: place to store block size
+ *
+ * nilfs_get_blocksize() calculates the block size from the block size
+ * exponent information written in @sbp and stores it in @blocksize,
+ * or aborts with an error message if it's too large.
+ *
+ * Return Value: On success, 0 is returned. If the block size is too
+ * large, -EINVAL is returned.
+ */
+static int nilfs_get_blocksize(struct super_block *sb,
+			       struct nilfs_super_block *sbp, int *blocksize)
+{
+	unsigned int shift_bits = le32_to_cpu(sbp->s_log_block_size);
+
+	if (unlikely(shift_bits >
+		     ilog2(NILFS_MAX_BLOCK_SIZE) - BLOCK_SIZE_BITS)) {
+		nilfs_err(sb, "too large filesystem blocksize: 2 ^ %u KiB",
+			  shift_bits);
+		return -EINVAL;
+	}
+	*blocksize = BLOCK_SIZE << shift_bits;
+	return 0;
+}
+
+/**
  * load_nilfs - load and recover the nilfs
  * @nilfs: the_nilfs structure to be released
  * @sb: super block instance used to recover past segment
@@ -245,11 +274,15 @@ int load_nilfs(struct the_nilfs *nilfs, struct super_block *sb)
 		nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
 
 		/* verify consistency between two super blocks */
-		blocksize = BLOCK_SIZE << le32_to_cpu(sbp[0]->s_log_block_size);
+		err = nilfs_get_blocksize(sb, sbp[0], &blocksize);
+		if (err)
+			goto scan_error;
+
 		if (blocksize != nilfs->ns_blocksize) {
 			nilfs_warn(sb,
 				   "blocksize differs between two super blocks (%d != %d)",
 				   blocksize, nilfs->ns_blocksize);
+			err = -EINVAL;
 			goto scan_error;
 		}
 
@@ -443,11 +476,33 @@ static int nilfs_valid_sb(struct nilfs_super_block *sbp)
 	return crc == le32_to_cpu(sbp->s_sum);
 }
 
-static int nilfs_sb2_bad_offset(struct nilfs_super_block *sbp, u64 offset)
+/**
+ * nilfs_sb2_bad_offset - check the location of the second superblock
+ * @sbp: superblock raw data buffer
+ * @offset: byte offset of second superblock calculated from device size
+ *
+ * nilfs_sb2_bad_offset() checks if the position on the second
+ * superblock is valid or not based on the filesystem parameters
+ * stored in @sbp.  If @offset points to a location within the segment
+ * area, or if the parameters themselves are not normal, it is
+ * determined to be invalid.
+ *
+ * Return Value: true if invalid, false if valid.
+ */
+static bool nilfs_sb2_bad_offset(struct nilfs_super_block *sbp, u64 offset)
 {
-	return offset < ((le64_to_cpu(sbp->s_nsegments) *
-			  le32_to_cpu(sbp->s_blocks_per_segment)) <<
-			 (le32_to_cpu(sbp->s_log_block_size) + 10));
+	unsigned int shift_bits = le32_to_cpu(sbp->s_log_block_size);
+	u32 blocks_per_segment = le32_to_cpu(sbp->s_blocks_per_segment);
+	u64 nsegments = le64_to_cpu(sbp->s_nsegments);
+	u64 index;
+
+	if (blocks_per_segment < NILFS_SEG_MIN_BLOCKS ||
+	    shift_bits > ilog2(NILFS_MAX_BLOCK_SIZE) - BLOCK_SIZE_BITS)
+		return true;
+
+	index = offset >> (shift_bits + BLOCK_SIZE_BITS);
+	do_div(index, blocks_per_segment);
+	return index < nsegments;
 }
 
 static void nilfs_release_super_block(struct the_nilfs *nilfs)
@@ -586,9 +641,11 @@ int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb, char *data)
 	if (err)
 		goto failed_sbh;
 
-	blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
-	if (blocksize < NILFS_MIN_BLOCK_SIZE ||
-	    blocksize > NILFS_MAX_BLOCK_SIZE) {
+	err = nilfs_get_blocksize(sb, sbp, &blocksize);
+	if (err)
+		goto failed_sbh;
+
+	if (blocksize < NILFS_MIN_BLOCK_SIZE) {
 		nilfs_err(sb,
 			  "couldn't mount because of unsupported filesystem blocksize %d",
 			  blocksize);