f2fs: fix to avoid memory leakage in f2fs_listxattr

In f2fs_listxattr, there is no boundary check before
memcpy e_name to buffer.
If the e_name_len is corrupted,
unexpected memory contents may be returned to the buffer.

Signed-off-by: Randall Huang <huangrandall@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: Randall Huang

fs/f2fs/xattr.c

@@ -539,8 +539,9 @@ int f2fs_getxattr(struct inode *inode, int index, const char *name,
 ssize_t f2fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 {
 	struct inode *inode = d_inode(dentry);
+	nid_t xnid = F2FS_I(inode)->i_xattr_nid;
 	struct f2fs_xattr_entry *entry;
-	void *base_addr;
+	void *base_addr, *last_base_addr;
 	int error = 0;
 	size_t rest = buffer_size;
 
@@ -550,13 +551,24 @@ ssize_t f2fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 	if (error)
 		return error;
 
+	last_base_addr = (void *)base_addr + XATTR_SIZE(xnid, inode);
+
 	list_for_each_xattr(entry, base_addr) {
 		const struct xattr_handler *handler =
 			f2fs_xattr_handler(entry->e_name_index);
 		const char *prefix;
 		size_t prefix_len;
 		size_t size;
 
+		if ((void *)(entry) + sizeof(__u32) > last_base_addr ||
+			(void *)XATTR_NEXT_ENTRY(entry) > last_base_addr) {
+			f2fs_err(F2FS_I_SB(inode), "inode (%lu) has corrupted xattr",
+						inode->i_ino);
+			set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK);
+			error = -EFSCORRUPTED;
+			goto cleanup;
+		}
+
 		if (!handler || (handler->list && !handler->list(dentry)))
 			continue;