From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org,
Christian Brauner <brauner@kernel.org>,
Christoph Hellwig <hch@lst.de>,
Namjae Jeon <linkinjeon@kernel.org>,
David Sterba <dsterba@suse.com>,
David Howells <dhowells@redhat.com>,
Miklos Szeredi <miklos@szeredi.hu>,
Amir Goldstein <amir73il@gmail.com>,
Trond Myklebust <trond.myklebust@hammerspace.com>,
Bob Peterson <rpeterso@redhat.com>,
Steve French <sfrench@samba.org>,
Luis Chamberlain <mcgrof@kernel.org>
Subject: Re: [PATCH 02/15] exfat: move freeing sbi, upcase table and dropping nls into rcu-delayed helper
Date: Mon, 2 Oct 2023 19:04:00 +0100 [thread overview]
Message-ID: <20231002180400.GY800259@ZenIV> (raw)
In-Reply-To: <CAHk-=wjDRb4OyO9ARykQWuC7GJmj1N0uKH-CghXgjW5ypdnQ4g@mail.gmail.com>
On Mon, Oct 02, 2023 at 09:10:22AM -0700, Linus Torvalds wrote:
> On Sun, 1 Oct 2023 at 19:30, Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > That stuff can be accessed by ->d_hash()/->d_compare(); as it is, we have
> > a hard-to-hit UAF if rcu pathwalk manages to get into ->d_hash() on a filesystem
> > that is in process of getting shut down.
> >
> > Besides, having nls and upcase table cleanup moved from ->put_super() towards
> > the place where sbi is freed makes for simpler failure exits.
>
> I don't disagree with moving the freeing, but the RCU-delay makes me go "hmm".
>
> Is there some reason why we can't try to do this in generic code? The
> umount code already does RCU delays for other things, I get the
> feeling that we should have a RCu delay between "put_super" and
> "kkill_sb".
>
> Could we move the ->kill_sb() call into destroy_super_work(), which is
> already RCU-delayed, for example?
>
> It feels wrong to have the filesystems have to deal with the vfs layer
> doing RCU-lookups.
For one thing, ->kill_sb() might do tons of IO. And we really want
to have that done before umount(2) returns to userland, so that part can't
be offloaded via schedule_work()...
next prev parent reply other threads:[~2023-10-02 18:04 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-02 2:28 [RFC][PATCHES] fixes in methods exposed to rcu pathwalk Al Viro
2023-10-02 2:28 ` Al Viro
2023-10-02 2:29 ` [PATCH 01/15] rcu pathwalk: prevent bogus hard errors from may_lookup() Al Viro
2023-10-02 2:30 ` [PATCH 02/15] exfat: move freeing sbi, upcase table and dropping nls into rcu-delayed helper Al Viro
2023-10-02 16:10 ` Linus Torvalds
2023-10-02 18:04 ` Al Viro [this message]
2023-10-02 2:30 ` [PATCH 03/15] affs: free affs_sb_info with kfree_rcu() Al Viro
2023-10-02 2:31 ` [PATCH 04/15] hfsplus: switch to rcu-delayed unloading of nls and freeing ->s_fs_info Al Viro
2023-10-02 6:49 ` Christoph Hellwig
2023-10-02 7:14 ` Al Viro
2023-10-02 7:21 ` Al Viro
2023-10-02 18:09 ` Al Viro
2023-10-04 19:04 ` Linus Torvalds
2023-10-04 19:06 ` Linus Torvalds
2023-10-02 2:31 ` [PATCH 05/15] cifs_get_link(): bail out in unsafe case Al Viro
2023-10-02 2:32 ` [PATCH 06/15] procfs: move dropping pde and pid from ->evict_inode() to ->free_inode() Al Viro
2023-10-02 2:33 ` [PATCH 07/15] procfs: make freeing proc_fs_info rcu-delayed Al Viro
2023-10-02 2:33 ` [PATCH 08/15] gfs2: fix an oops in gfs2_permission() Al Viro
2023-10-02 11:46 ` Bob Peterson
2023-10-02 12:59 ` Al Viro
2023-10-02 14:16 ` Al Viro
2023-10-03 14:46 ` Andreas Grünbacher
2023-10-02 2:34 ` [PATCH 09/15] nfs: make nfs_set_verifier() safe for use in RCU pathwalk Al Viro
2023-10-02 2:34 ` [PATCH 10/15] nfs: fix UAF on pathwalk running into umount Al Viro
2023-10-02 2:35 ` [PATCH 11/15] fuse: fix UAF in rcu pathwalks Al Viro
2023-10-02 2:35 ` [PATCH 12/15] afs: fix __afs_break_callback() / afs_drop_open_mmap() race Al Viro
2023-10-02 2:36 ` [PATCH 13/15] overlayfs: move freeing ovl_entry past rcu delay Al Viro
2023-10-02 2:36 ` [PATCH 14/15] ovl_dentry_revalidate_common(): fetch inode once Al Viro
2023-10-02 2:37 ` [PATCH 15/15] overlayfs: make use of ->layers safe in rcu pathwalk Al Viro
2023-10-02 6:40 ` Amir Goldstein
2023-10-02 7:23 ` Al Viro
2023-10-02 8:53 ` Amir Goldstein
2023-10-03 20:47 ` Al Viro
2023-10-02 5:47 ` [PATCH 14/15] ovl_dentry_revalidate_common(): fetch inode once Amir Goldstein
2023-10-02 5:56 ` Amir Goldstein
2023-10-02 14:47 ` Amir Goldstein
2023-10-02 5:51 ` [PATCH 13/15] overlayfs: move freeing ovl_entry past rcu delay Amir Goldstein
2023-10-02 2:52 ` [RFC][PATCHES] fixes in methods exposed to rcu pathwalk Al Viro
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