From: "J. Bruce Fields" <bfields@fieldses.org>
To: Pan Bian <bianpan2016@163.com>
Cc: Amir Goldstein <amir73il@gmail.com>,
Miklos Szeredi <mszeredi@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>, Christoph Hellwig <hch@lst.de>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V2] exportfs: do not read dentry after free
Date: Fri, 23 Nov 2018 22:48:52 -0500 [thread overview]
Message-ID: <20181124034852.GD7489@fieldses.org> (raw)
In-Reply-To: <1542959793-118334-1-git-send-email-bianpan2016@163.com>
On Fri, Nov 23, 2018 at 03:56:33PM +0800, Pan Bian wrote:
> The function dentry_connected calls dput(dentry) to drop the previously
> acquired reference to dentry. In this case, dentry can be released.
> After that, IS_ROOT(dentry) checks the condition
> (dentry == dentry->d_parent), which may result in a use-after-free bug.
> This patch directly compares dentry with its parent obtained before
> dropping the reference.
Looks right to me, thanks.--b.
>
> Fixes: a056cc8934c("exportfs: stop retrying once we race with
> rename/remove")
>
> Signed-off-by: Pan Bian <bianpan2016@163.com>
>
> ---
> V2: get rid of the comment
>
> ---
> fs/exportfs/expfs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
> index 645158d..a69aaf5 100644
> --- a/fs/exportfs/expfs.c
> +++ b/fs/exportfs/expfs.c
> @@ -77,7 +77,7 @@ static bool dentry_connected(struct dentry *dentry)
> struct dentry *parent = dget_parent(dentry);
>
> dput(dentry);
> - if (IS_ROOT(dentry)) {
> + if (dentry == parent) {
> dput(parent);
> return false;
> }
> --
> 2.7.4
>
prev parent reply other threads:[~2018-11-24 3:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-23 7:56 [PATCH V2] exportfs: do not read dentry after free Pan Bian
2018-11-23 14:07 ` Al Viro
2018-11-24 3:48 ` J. Bruce Fields [this message]
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