linux-ext4 - Re: return an ERR_PTR from __filemap_get

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20230121170641.121f4224a0e8304765bb4738@linux-foundation.org>
Date:   Sat, 21 Jan 2023 17:06:41 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Hugh Dickins <hughd@...gle.com>, linux-afs@...ts.infradead.org,
        linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        cluster-devel@...hat.com, linux-mm@...ck.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-nilfs@...r.kernel.org
Subject: Re: return an ERR_PTR from __filemap_get_folio v2

On Sat, 21 Jan 2023 07:57:48 +0100 Christoph Hellwig <hch@....de> wrote:

> Hi all,
> 
> __filemap_get_folio and its wrappers can return NULL for three different
> conditions, which in some cases requires the caller to reverse engineer
> the decision making.  This is fixed by returning an ERR_PTR instead of
> NULL and thus transporting the reason for the failure.  But to make
> that work we first need to ensure that no xa_value special case is
> returned and thus return the FGP_ENTRY flag.  It turns out that flag
> is barely used and can usually be deal with in a better way.
> 
> Note that the shmem patches in here are non-trivial and need some
> careful review and testing.

I'll hide for a while, awaiting that review.  Plus...

> Changes since v1:
>  - drop the patches to check for errors in btrfs and gfs2
>  - document the new calling conventions for the wrappers around
>    __filemap_get_folio
>  - rebased against the iomap changes in latest linux-next

This patchset doesn't apply to fs/btrfs/ because linux-next contains
this 6+ month-old commit:

commit 964688b32d9ada55a7fce2e650d85ef24188f73f                
Author:     Matthew Wilcox (Oracle) <willy@...radead.org>
AuthorDate: Tue May 17 18:03:27 2022 -0400
Commit:     Matthew Wilcox (Oracle) <willy@...radead.org>
CommitDate: Wed Jun 29 08:51:07 2022 -0400

    btrfs: Use a folio in wait_dev_supers()


Matthew, what's the story here?