linux-kernel - Re: [PATCH] fs/9p: Compare qid.path in v9fs_test

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Date:   Thu, 9 Mar 2017 11:26:18 -0600
From:   Latchesar Ionkov <lucho@...kov.net>
To:     Tuomas Tynkkynen <tuomas@...era.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org,
        Eric Van Hensbergen <ericvh@...il.com>,
        V9FS Developers <v9fs-developer@...ts.sourceforge.net>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH] fs/9p: Compare qid.path in v9fs_test_inode

Reviewed-by: Latchesar Ionkov <lucho@...kov.net>


On Tue, Feb 21, 2017 at 6:06 PM, Tuomas Tynkkynen <tuomas@...era.com> wrote:
> Commit fd2421f54423 ("fs/9p: When doing inode lookup compare qid details
> and inode mode bits.") transformed v9fs_qid_iget() to use iget5_locked()
> instead of iget_locked(). However, the test() callback is not checking
> fid.path at all, which means that a lookup in the inode cache can now
> accidentally locate a completely wrong inode from the same inode hash
> bucket if the other fields (qid.type and qid.version) match.
>
> Fixes: fd2421f54423 ("fs/9p: When doing inode lookup compare qid details and inode mode bits.")
> Cc: stable@...r.kernel.org
> Signed-off-by: Tuomas Tynkkynen <tuomas@...era.com>
> ---
> Does this sound sensible? I have never reproduced the problem myself but
> reportedly this patch solves some really weird problems where the
> symptoms match (wrong files being opened unpredictably).
> ---
>  fs/9p/vfs_inode.c      | 3 +++
>  fs/9p/vfs_inode_dotl.c | 3 +++
>  2 files changed, 6 insertions(+)
>
> diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
> index 30ca770c5e0b..f8ab4a66acaf 100644
> --- a/fs/9p/vfs_inode.c
> +++ b/fs/9p/vfs_inode.c
> @@ -483,6 +483,9 @@ static int v9fs_test_inode(struct inode *inode, void *data)
>
>         if (v9inode->qid.type != st->qid.type)
>                 return 0;
> +
> +       if (v9inode->qid.path != st->qid.path)
> +               return 0;
>         return 1;
>  }
>
> diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
> index afaa4b6de801..c3dd0d42bb3a 100644
> --- a/fs/9p/vfs_inode_dotl.c
> +++ b/fs/9p/vfs_inode_dotl.c
> @@ -87,6 +87,9 @@ static int v9fs_test_inode_dotl(struct inode *inode, void *data)
>
>         if (v9inode->qid.type != st->qid.type)
>                 return 0;
> +
> +       if (v9inode->qid.path != st->qid.path)
> +               return 0;
>         return 1;
>  }
>
> --
> 2.11.1
>