erofs: fix double free of 'copied'

Dan reported a new smatch warning [1]
"fs/erofs/inode.c:210 erofs_read_inode() error: double free of 'copied'"

Due to new chunk-based format handling logic, the error path can be
called after kfree(copied).

Set "copied = NULL" after kfree(copied) to fix this.

[1] https://lore.kernel.org/r/[email protected]

Link: https://lore.kernel.org/r/[email protected]
Fixes: c5aa903 ("erofs: support reading chunk-based uncompressed files")
Reported-by: kernel test robot <[email protected]>
Reported-by: Dan Carpenter <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Gao Xiang <[email protected]>

Author: hsiangkao

fs/erofs/inode.c

@@ -127,6 +127,7 @@ static struct page *erofs_read_inode(struct inode *inode,
 			/* fill chunked inode summary info */
 			vi->chunkformat = le16_to_cpu(die->i_u.c.format);
 		kfree(copied);
+		copied = NULL;
 		break;
 	case EROFS_INODE_LAYOUT_COMPACT:
 		vi->inode_isize = sizeof(struct erofs_inode_compact);