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Message-ID: <20231002064646.GA1799@lst.de> Date: Mon, 2 Oct 2023 08:46:46 +0200 From: Christoph Hellwig <hch@....de> To: Al Viro <viro@...iv.linux.org.uk> Cc: Christoph Hellwig <hch@....de>, Christian Brauner <brauner@...nel.org>, Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, Alexander Gordeev <agordeev@...ux.ibm.com>, Fenghua Yu <fenghua.yu@...el.com>, Reinette Chatre <reinette.chatre@...el.com>, Miquel Raynal <miquel.raynal@...tlin.com>, Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>, Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>, Tejun Heo <tj@...nel.org>, Trond Myklebust <trond.myklebust@...merspace.com>, Anna Schumaker <anna@...nel.org>, Kees Cook <keescook@...omium.org>, Damien Le Moal <dlemoal@...nel.org>, Naohiro Aota <naohiro.aota@....com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org, linux-nfs@...r.kernel.org, linux-hardening@...r.kernel.org, cgroups@...r.kernel.org Subject: Re: [PATCH 03/19] fs: release anon dev_t in deactivate_locked_super On Tue, Sep 26, 2023 at 10:25:15PM +0100, Al Viro wrote: > Before your patch: foo_kill_super() calls kill_anon_super(), > which calls kill_super_notify(), which removes the sucker from > the list, then frees ->s_fs_info. After your patch: > removal from the lists happens via the call of kill_super_notify() > *after* both of your methods had been called, while freeing > ->s_fs_info happens from the method call. IOW, you've restored > the situation prior to "super: ensure valid info". The whole > point of that commit had been to make sure that we have nothing > in the lists with ->s_fs_info pointing to a freed object. > > It's not about free_anon_bdev(); that part is fine - it's the > "we can drop the weird second call site of kill_super_notify()" > thing that is broken. The point has been to only release the anon dev_t after kill_super_notify, to prevent two of them beeing reused. Which we do as the free_anon_bdev is done directly in deactivate_locked_super. The new ->free_sb for non-block file systems frees resources, but none of them matter for sget.
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