Merge pull request #160 from microsoft/wedsonaf/tardev

tarfs reliability fixes

src/tarfs/tarfs.c

@@ -98,39 +98,44 @@ static int tarfs_readdir(struct file *file, struct dir_context *ctx)
 	int ret = 0;
 	char *name_buffer = NULL;
 	u64 name_len = 0;
-	u64 cur = ctx->pos;
 	u64 size = i_size_read(inode) / sizeof(disk_dentry) * sizeof(disk_dentry);
+	loff_t orig_pos = ctx->pos;
 
-	/* cur must be aligned to a directory entry. */
+	/* ctx->pos must be aligned to a directory entry. */
 	if (ctx->pos % sizeof(struct tarfs_direntry))
 		return -ENOENT;
 
 	/* Make sure we can't overflow the read offset. */
 	if (offset + size < offset)
 		return -ERANGE;
 
-	/* Make sure the increment of cur won't overflow by limiting size. */
+	/* Make sure the increment of ctx->pos won't overflow by limiting size. */
 	if (size >= U64_MAX - sizeof(disk_dentry))
 		return -ERANGE;
 
-	for (cur = ctx->pos; cur < size; cur += sizeof(disk_dentry)) {
+	for (; ctx->pos < size; ctx->pos += sizeof(disk_dentry)) {
 		u64 disk_len;
 		u8 type;
 
-		ret = tarfs_dev_read(inode->i_sb, offset + cur, &disk_dentry, sizeof(disk_dentry));
+		ret = tarfs_dev_read(inode->i_sb, offset + ctx->pos, &disk_dentry, sizeof(disk_dentry));
 		if (ret)
 			break;
 
 		disk_len = le64_to_cpu(disk_dentry.namelen);
 		if (disk_len > name_len) {
 			kfree(name_buffer);
-
-			if (disk_len > SIZE_MAX)
-				return -ENOMEM;
-
-			name_buffer = kmalloc(disk_len, GFP_KERNEL);
-			if (!name_buffer)
-				return -ENOMEM;
+			name_buffer = NULL;
+
+			if (disk_len > SIZE_MAX) {
+				ret = -ENOMEM;
+				break;
+			}
+
+			name_buffer = kmalloc(disk_len, GFP_NOFS);
+			if (!name_buffer) {
+				ret = -ENOMEM;
+				break;
+			}
 			name_len = disk_len;
 		}
 
@@ -162,11 +167,7 @@ static int tarfs_readdir(struct file *file, struct dir_context *ctx)
 	}
 
 	kfree(name_buffer);
-
-	if (!ret)
-		ctx->pos = cur;
-
-	return ret;
+	return ctx->pos != orig_pos ? 0 : ret;
 }
 
 static int tarfs_readpage(struct file *file, struct page *page)
@@ -178,8 +179,11 @@ static int tarfs_readpage(struct file *file, struct page *page)
 	int ret;
 
 	buf = kmap_local_page(page);
-	if (!buf)
+	if (!buf) {
+		SetPageError(page);
+		unlock_page(page);
 		return -ENOMEM;
+	}
 
 	offset = page_offset(page);
 	size = i_size_read(inode);
@@ -331,19 +335,24 @@ static struct inode *tarfs_iget(struct super_block *sb, u64 ino)
 	return inode;
 
 discard:
-	discard_new_inode(inode);
+	iget_failed(inode);
 	return ERR_PTR(ret);
 }
 
-static int tarfs_strcmp(struct super_block *sb, unsigned long pos,
-			    const char *str, size_t size)
+static int tarfs_strcmp(struct super_block *sb, u64 pos, const char *str,
+			size_t size)
 {
 	struct buffer_head *bh;
 	unsigned long offset;
 	size_t segment;
 	bool matched;
+	const struct tarfs_state *state = sb->s_fs_info;
+
+	/* If the string doesn't fit in the data size, it doesn't match. */
+	if (pos + size < pos || pos + size > state->data_size)
+		return 0;
 
-	/* compare string up to a block at a time. */
+	/* Compare string up to a block at a time. */
 	while (size) {
 		offset = pos & (TARFS_BSIZE - 1);
 		segment = min_t(size_t, size, TARFS_BSIZE - offset);
@@ -448,7 +457,7 @@ static struct inode *tarfs_alloc_inode(struct super_block *sb)
 {
 	struct tarfs_inode_info *info;
 
-        info = alloc_inode_sb(sb, tarfs_inode_cachep, GFP_KERNEL);
+        info = alloc_inode_sb(sb, tarfs_inode_cachep, GFP_NOFS);
         if (!info)
                 return NULL;
 
@@ -514,7 +523,7 @@ static int tarfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	sb->s_xattr = xattr_handlers;
 
 	scount = bdev_nr_sectors(sb->s_bdev);
-	if (!scount)
+	if (scount < TARFS_BSIZE / SECTOR_SIZE)
 		return -ENXIO;
 
 	state = kmalloc(sizeof(*state), GFP_KERNEL);