fix wrong inode size for rev#0 ext2fs

extfs.c assumes that there is always a valid inode_size field in the
superblock. But this is not true for ext2fs rev 0. Such ext2fs images are for
instance generated by genext2fs. Symptoms on ARM machines can be messages like:
"raise: Signal # 8 caught"
This fix checks for rev 0 and uses then 128 bytes as inode size.

1 files changed, 13 insertions, 7 deletions

diff --git a/fs/ext2/ext2fs.c b/fs/ext2/ext2fs.c
index d54f60b30..4b391d60a 100644
--- a/fs/ext2/ext2fs.c
+++ b/fs/ext2/ext2fs.c
@@ -178,6 +178,7 @@ int indir1_blkno = -1;
 uint32_t *indir2_block = NULL;
 int indir2_size = 0;
 int indir2_blkno = -1;
+static unsigned int inode_size;
 
 
 static int ext2fs_blockgroup
@@ -212,7 +213,7 @@ static int ext2fs_read_inode
 	unsigned int blkoff;
 
 #ifdef DEBUG
-	printf ("ext2fs read inode %d\n", ino);
+	printf ("ext2fs read inode %d, inode_size %d\n", ino, inode_size);
 #endif
 	/* It is easier to calculate if the first inode is 0.  */
 	ino--;
@@ -222,16 +223,12 @@ static int ext2fs_read_inode
 		return (0);
 	}
 
-	inodes_per_block = EXT2_BLOCK_SIZE(data) / __le16_to_cpu(sblock->inode_size);
-
-#ifdef DEBUG
-	printf ("ext2fs read inode blkno %d blkoff %d\n", blkno, blkoff);
-#endif
+	inodes_per_block = EXT2_BLOCK_SIZE(data) / inode_size;
 
 	blkno = __le32_to_cpu (blkgrp.inode_table_id) +
 		(ino % __le32_to_cpu (sblock->inodes_per_group))
 		/ inodes_per_block;
-	blkoff = (ino % inodes_per_block) * __le16_to_cpu (sblock->inode_size);
+	blkoff = (ino % inodes_per_block) * inode_size;
 #ifdef DEBUG
 	printf ("ext2fs read inode blkno %d blkoff %d\n", blkno, blkoff);
 #endif
@@ -863,6 +860,15 @@ int ext2fs_mount (unsigned part_length) {
 	if (__le16_to_cpu (data->sblock.magic) != EXT2_MAGIC) {
 		goto fail;
 	}
+	if (__le32_to_cpu(data->sblock.revision_level == 0)) {
+		inode_size = 128;
+	} else {
+		inode_size = __le16_to_cpu(data->sblock.inode_size);
+	}
+#ifdef DEBUG
+	printf("EXT2 rev %d, inode_size %d\n",
+			__le32_to_cpu(data->sblock.revision_level), inode_size);
+#endif
 	data->diropen.data = data;
 	data->diropen.ino = 2;
 	data->diropen.inode_read = 1;