From: Jan Kara <jack@suse.cz>
To: Miklos Szeredi <mszeredi@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, Jan Kara <jack@suse.cz>,
Amir Goldstein <amir73il@gmail.com>,
Xiong Zhou <xzhou@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/7] fsnotify: pin both inode and vfsmount mark
Date: Mon, 30 Oct 2017 14:34:38 +0100 [thread overview]
Message-ID: <20171030133438.GK23278@quack2.suse.cz> (raw)
In-Reply-To: <1508920899-8115-3-git-send-email-mszeredi@redhat.com>
On Wed 25-10-17 10:41:34, Miklos Szeredi wrote:
> We may fail to pin one of the marks in fsnotify_prepare_user_wait() when
> dropping the srcu read lock, resulting in use after free at the next
> iteration.
>
> Solution is to store both marks in iter_info instead of just the one we'll
> be sending the event for.
I'm sorry but I'm not getting it. Where exactly is use-after-free
happening? And how come because if fsnotify_prepare_user_wait() fails to
pin some mark, it does not drop SRCU and bails out, doesn't it?
Honza
> diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
> index 0c4583b61717..48ec61f4c4d5 100644
> --- a/fs/notify/fsnotify.c
> +++ b/fs/notify/fsnotify.c
> @@ -336,6 +336,9 @@ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
> vfsmount_group = vfsmount_mark->group;
> }
>
> + iter_info.inode_mark = inode_mark;
> + iter_info.vfsmount_mark = vfsmount_mark;
> +
> if (inode_group && vfsmount_group) {
> int cmp = fsnotify_compare_groups(inode_group,
> vfsmount_group);
> @@ -348,9 +351,6 @@ int fsnotify(struct inode *to_tell, __u32 mask, const void *data, int data_is,
> }
> }
>
> - iter_info.inode_mark = inode_mark;
> - iter_info.vfsmount_mark = vfsmount_mark;
> -
> ret = send_to_group(to_tell, inode_mark, vfsmount_mark, mask,
> data, data_is, cookie, file_name,
> &iter_info);
> --
> 2.5.5
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2017-10-30 13:34 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-25 8:41 [PATCH v2 0/7] fix fanotify issues with the series in v4.12 Miklos Szeredi
2017-10-25 8:41 ` [PATCH v2 1/7] fsnotify: clean up fsnotify_prepare/finish_user_wait() Miklos Szeredi
2017-10-25 12:06 ` Amir Goldstein
2017-10-25 12:07 ` Amir Goldstein
2017-10-25 14:15 ` Miklos Szeredi
2017-10-25 8:41 ` [PATCH v2 2/7] fsnotify: pin both inode and vfsmount mark Miklos Szeredi
2017-10-30 13:34 ` Jan Kara [this message]
2017-10-30 13:42 ` Miklos Szeredi
2017-10-30 14:05 ` Jan Kara
2017-10-25 8:41 ` [PATCH v2 3/7] fsnotify: fix pinning group in fsnotify_prepare_user_wait() Miklos Szeredi
2017-10-25 8:41 ` [PATCH v2 4/7] fsnotify: skip unattached marks Miklos Szeredi
2017-10-30 14:00 ` Jan Kara
2017-10-30 14:27 ` Miklos Szeredi
2017-10-25 8:41 ` [PATCH v2 5/7] fanotify: fix fsnotify_prepare_user_wait() failure Miklos Szeredi
2017-10-25 8:41 ` [PATCH v2 6/7] fsnotify: clean up fsnotify() Miklos Szeredi
2017-10-25 11:46 ` Amir Goldstein
2017-10-25 8:41 ` [PATCH v2 7/7] fanotify: clean up CONFIG_FANOTIFY_ACCESS_PERMISSIONS ifdefs Miklos Szeredi
2017-10-25 11:44 ` Amir Goldstein
2017-10-25 14:19 ` Miklos Szeredi
2017-10-30 17:20 ` Jan Kara
2017-10-25 14:31 ` [PATCH v2 0/7] fix fanotify issues with the series in v4.12 Miklos Szeredi
2017-10-25 15:13 ` Amir Goldstein
2017-10-27 11:53 ` Jan Kara
2017-10-30 15:56 ` Miklos Szeredi
2017-10-30 17:27 ` Jan Kara
2017-10-30 20:18 ` Miklos Szeredi
2017-10-31 9:54 ` Jan Kara
2017-10-31 11:02 ` Amir Goldstein
2017-10-31 16:27 ` Jan Kara
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