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Message-ID: <20180406021553.GS30522@ZenIV.linux.org.uk> Date: Fri, 6 Apr 2018 03:15:53 +0100 From: Al Viro <viro@...IV.linux.org.uk> To: Christoph Hellwig <hch@....de> Cc: Avi Kivity <avi@...lladb.com>, linux-aio@...ck.org, linux-fsdevel@...r.kernel.org, netdev@...r.kernel.org, linux-api@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 08/32] aio: replace kiocb_set_cancel_fn with a cancel_kiocb file operation On Fri, Mar 30, 2018 at 05:07:45PM +0200, Christoph Hellwig wrote: > The current kiocb_set_cancel_fn implementation assumes the kiocb is > embedded into an aio_kiocb, which is fundamentally unsafe as it might > have been submitted by non-aio callers. Instead add a cancel_kiocb > file operation that replaced the ki_cancel function pointer set by > kiocb_set_cancel_fn, and only adds iocbs to the active list when > the read/write_iter methods return -EIOCBQUEUED and the file has > a cancel_kiocb method. > @@ -1440,6 +1423,16 @@ static inline ssize_t aio_rw_ret(struct kiocb *req, ssize_t ret) > { > switch (ret) { > case -EIOCBQUEUED: > + if (req->ki_filp->f_op->cancel_kiocb) { ... and by that point req might've been already freed by IO completion on another CPU. > + struct aio_kiocb *iocb = > + container_of(req, struct aio_kiocb, rw); > + struct kioctx *ctx = iocb->ki_ctx; > + unsigned long flags; > + > + spin_lock_irqsave(&ctx->ctx_lock, flags); > + list_add_tail(&iocb->ki_list, &ctx->active_reqs);
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