From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F09A37869E; Mon, 4 Mar 2024 19:31:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709580716; cv=none; b=m2JJ0HJANmG4TMHPQwkO1lxcp/CaNgNxaNVtSNzfE5J0FpRAib8HG+28GUoHvMaO/EPzmCmeGFOwmsv7ks/VyUuVRXt9k8t7fTDP7CDBtSvGgf3o34xzvv1KkTGX8+f7M9ue642UqsQu6tOBvK22XReRlWQw4F2X2bGtS+dGTfE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709580716; c=relaxed/simple; bh=/7r2yABS70a2BV6XpcMn72U5TYLEICOD6PuGQ6u/XDI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=o6iwOTnYHru8fzzwBX9NpESVwJjLpAXWAOqSqqqpnnTDU25EpFz71VqEX4QmsohL/pepiYyfdhyig/64ezUIIrRukFXc4ovWICQvitLKLMgQanETjDU4F62rM+I8WnvjLoL0a2L12+oNJwdXwoX5lNTLcNQ+cmT1IO1AVldRj9Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HL9BNOn9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HL9BNOn9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 206BFC433F1; Mon, 4 Mar 2024 19:31:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1709580715; bh=/7r2yABS70a2BV6XpcMn72U5TYLEICOD6PuGQ6u/XDI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HL9BNOn9j3nsV+vEwAQlzNMLVlrtDdXS4J70mNXFp/uhEqJNvhwYWN/WvW4mZzKHG UIXYq+hr5UgxJAoLvD7sSeWUOP438JXs/NOicgbWXu8zeLCtLyjIJRGU5918hNnMmb SXLFapzROq83bPtEHBJUGBY3RLgCJQjxchAmRLbrDybSp4r/pNdBqAVXN1nF3WrYfi YGVPJ3xN46B9mZ1LQHMh4yWUfJY5SMwpoNxJZf2+AsJTCjuCvhhy/J8Gnph+tl+tw/ jmDhc5fk/Ep3wMIUNS7vQSP9ruXaT9W2VgfT43DjOD0v4003LRSn/W7pzwIC61xhof judK6rA9UFsiw== Date: Mon, 4 Mar 2024 11:31:53 -0800 From: Eric Biggers To: Bart Van Assche Cc: Christian Brauner , linux-fsdevel@vger.kernel.org, Christoph Hellwig , Benjamin LaHaise , Avi Kivity , Sandeep Dhavale , Jens Axboe , Greg Kroah-Hartman , Kent Overstreet , stable@vger.kernel.org, syzbot+b91eb2ed18f599dd3c31@syzkaller.appspotmail.com Subject: Re: [PATCH] Revert "fs/aio: Make io_cancel() generate completions again" Message-ID: <20240304193153.GC1195@sol.localdomain> References: <20240304182945.3646109-1-bvanassche@acm.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240304182945.3646109-1-bvanassche@acm.org> On Mon, Mar 04, 2024 at 10:29:44AM -0800, Bart Van Assche wrote: > Patch "fs/aio: Make io_cancel() generate completions again" is based on the > assumption that calling kiocb->ki_cancel() does not complete R/W requests. > This is incorrect: the two drivers that call kiocb_set_cancel_fn() callers > set a cancellation function that calls usb_ep_dequeue(). According to its > documentation, usb_ep_dequeue() calls the completion routine with status > -ECONNRESET. Hence this revert. > > Cc: Benjamin LaHaise > Cc: Eric Biggers > Cc: Christoph Hellwig > Cc: Avi Kivity > Cc: Sandeep Dhavale > Cc: Jens Axboe > Cc: Greg Kroah-Hartman > Cc: Kent Overstreet > Cc: stable@vger.kernel.org > Reported-by: syzbot+b91eb2ed18f599dd3c31@syzkaller.appspotmail.com > Fixes: 54cbc058d86b ("fs/aio: Make io_cancel() generate completions again") > Signed-off-by: Bart Van Assche > --- > fs/aio.c | 27 ++++++++++++++++----------- > 1 file changed, 16 insertions(+), 11 deletions(-) > > diff --git a/fs/aio.c b/fs/aio.c > index 28223f511931..da18dbcfcb22 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -2165,11 +2165,14 @@ COMPAT_SYSCALL_DEFINE3(io_submit, compat_aio_context_t, ctx_id, > #endif > > /* sys_io_cancel: > - * Attempts to cancel an iocb previously passed to io_submit(). If the > - * operation is successfully cancelled 0 is returned. May fail with > - * -EFAULT if any of the data structures pointed to are invalid. May > - * fail with -EINVAL if aio_context specified by ctx_id is invalid. Will > - * fail with -ENOSYS if not implemented. > + * Attempts to cancel an iocb previously passed to io_submit. If > + * the operation is successfully cancelled, the resulting event is > + * copied into the memory pointed to by result without being placed > + * into the completion queue and 0 is returned. May fail with > + * -EFAULT if any of the data structures pointed to are invalid. > + * May fail with -EINVAL if aio_context specified by ctx_id is > + * invalid. May fail with -EAGAIN if the iocb specified was not > + * cancelled. Will fail with -ENOSYS if not implemented. > */ > SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb, > struct io_event __user *, result) > @@ -2200,12 +2203,14 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb, > } > spin_unlock_irq(&ctx->ctx_lock); > > - /* > - * The result argument is no longer used - the io_event is always > - * delivered via the ring buffer. > - */ > - if (ret == 0 && kiocb->rw.ki_flags & IOCB_AIO_RW) > - aio_complete_rw(&kiocb->rw, -EINTR); > + if (!ret) { > + /* > + * The result argument is no longer used - the io_event is > + * always delivered via the ring buffer. -EINPROGRESS indicates > + * cancellation is progress: > + */ > + ret = -EINPROGRESS; > + } Acked-by: Eric Biggers It does look like all the ->ki_cancel functions complete the request already, so this patch was unnecessary and just introduced a bug. Note that IOCB_CMD_POLL installs a ->ki_cancel function too, and that's how syzbot hit the use-after-free so easily. I assume that the patch just wasn't tested? Or did you find that it actually fixed something (how)? By the way, libaio (https://pagure.io/libaio) has a test suite for these system calls. How about adding a test case that cancels an IOCB_CMD_POLL request and verifies that the completion event is received? - Eric