udf: Return -ENOMEM when allocation fails in udf_get_filename()

Return -ENOMEM when allocation fails in udf_get_filename(). Update
udf_pc_to_char(), udf_readdir(), and udf_find_entry() to handle the
error appropriately. This allows us to pass appropriate error to
userspace instead of corrupting symlink contents by omitting some path
elements.
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/dir.c

@@ -168,7 +168,7 @@ static int udf_readdir(struct file *file, struct dir_context *ctx)
 		}
 
 		flen = udf_get_filename(sb, nameptr, lfi, fname, UDF_NAME_LEN);
-		if (!flen)
+		if (flen <= 0)
 			continue;
 
 		tloc = lelb_to_cpu(cfi.icb.extLocation);

fs/udf/namei.c

@@ -234,7 +234,7 @@ static struct fileIdentDesc *udf_find_entry(struct inode *dir,
 			continue;
 
 		flen = udf_get_filename(sb, nameptr, lfi, fname, UDF_NAME_LEN);
-		if (flen && udf_match(flen, fname, child->len, child->name))
+		if (flen > 0 && udf_match(flen, fname, child->len, child->name))
 			goto out_ok;
 	}
 

fs/udf/symlink.c

@@ -82,6 +82,9 @@ static int udf_pc_to_char(struct super_block *sb, unsigned char *from,
 			comp_len = udf_get_filename(sb, pc->componentIdent,
 						    pc->lengthComponentIdent,
 						    p, tolen);
+			if (comp_len < 0)
+				return comp_len;
+
 			p += comp_len;
 			tolen -= comp_len;
 			if (tolen == 0)

fs/udf/unicode.c

@@ -338,15 +338,17 @@ int udf_get_filename(struct super_block *sb, uint8_t *sname, int slen,
 		     uint8_t *dname, int dlen)
 {
 	struct ustr *filename, *unifilename;
-	int len = 0;
+	int ret = 0;
 
 	filename = kmalloc(sizeof(struct ustr), GFP_NOFS);
 	if (!filename)
-		return 0;
+		return -ENOMEM;
 
 	unifilename = kmalloc(sizeof(struct ustr), GFP_NOFS);
-	if (!unifilename)
+	if (!unifilename) {
+		ret = -ENOMEM;
 		goto out1;
+	}
 
 	if (udf_build_ustr_exact(unifilename, sname, slen))
 		goto out2;
@@ -367,14 +369,14 @@ int udf_get_filename(struct super_block *sb, uint8_t *sname, int slen,
 	} else
 		goto out2;
 
-	len = udf_translate_to_linux(dname, dlen,
+	ret = udf_translate_to_linux(dname, dlen,
 				     filename->u_name, filename->u_len,
 				     unifilename->u_name, unifilename->u_len);
 out2:
 	kfree(unifilename);
 out1:
 	kfree(filename);
-	return len;
+	return ret;
 }
 
 int udf_put_filename(struct super_block *sb, const uint8_t *sname,