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From: Amir Goldstein <amir73il@gmail.com>
Date: Wed, 6 Mar 2024 12:18:30 +0200
Message-ID: <CAOQ4uxgi8sL3Dxznrq2tM76yMz_wTxh2PLzMd_Y-8ahWAhz=JQ@mail.gmail.com>
Subject: Re: [PATCH 11/13] fuse: fix UAF in rcu pathwalks
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Christian Brauner <brauner@kernel.org>, Al Viro <viro@zeniv.linux.org.uk>, 
	linux-fsdevel@vger.kernel.org, Linus Torvalds <torvalds@linux-foundation.org>, 
	linux-ext4@vger.kernel.org, linux-nfs@vger.kernel.org, 
	linux-cifs@vger.kernel.org
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On Tue, Mar 5, 2024 at 2:43=E2=80=AFPM Miklos Szeredi <miklos@szeredi.hu> w=
rote:
>
> On Mon, 4 Mar 2024 at 15:36, Amir Goldstein <amir73il@gmail.com> wrote:
>
> > Note that fuse_backing_files_free() calls
> > fuse_backing_id_free() =3D> fuse_backing_free() =3D> kfree_rcu()
> >
> > Should we move fuse_backing_files_free() into
> > fuse_conn_put() above fuse_dax_conn_free()?
> >
> > That will avoid the merge conflict and still be correct. no?
>
> Looks like a good cleanup.
>
> Force-pushed to fuse.git#for-next.
>

FYI, the version that you pushed will generate a minor conflict with

                }
-               fc->release(fc);
+               call_rcu(&fc->rcu, delayed_release);
        }
 }
 EXPORT_SYMBOL_GPL(fuse_conn_put);

If you move fuse_backing_files_free() to the start of the function,
I think merge conflict will be avoided:

 void fuse_conn_put(struct fuse_conn *fc)
 {
        if (refcount_dec_and_test(&fc->count)) {
                struct fuse_iqueue *fiq =3D &fc->iq;
                struct fuse_sync_bucket *bucket;

+               if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
+                       fuse_backing_files_free(fc);
                if (IS_ENABLED(CONFIG_FUSE_DAX))
                        fuse_dax_conn_free(fc);


Thanks,
Amir.