linux-kernel - Re: [PATCH v2] fs/inode.c: change the order of initialization in inode_init

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Date:   Thu, 1 Sep 2022 00:59:46 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Rustam Subkhankulov <subkhankulov@...ras.ru>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        ldv-project@...uxtesting.org
Subject: Re: [PATCH v2] fs/inode.c: change the order of initialization in
 inode_init_always()

On Mon, Aug 29, 2022 at 10:25:21PM +0300, Rustam Subkhankulov wrote:
> If function security_inode_alloc() returns a nonzero value due to an
> error (e.g. fail to allocate memory), then some of the fields, including
> 'i_private', will not be initialized.
> 
> After that, if the fs-specfic free_inode function is called in
> i_callback(), the nonzero value of 'i_private' field can be interpreted
> as initialized. As a result, this can cause dereferencing of random
> value pointer (e.g. nilfs2).
> 
> In earlier versions, a similar situation could occur with the 'u' union
> in 'inode' structure.

See vfs.git#work.inode (included into #for-next); I agree that your
commit message looks better, but...