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(No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2755F3082B07; Tue, 16 Jul 2019 14:57:23 +0000 (UTC) Received: from [10.18.17.130] (dhcp-17-130.bos.redhat.com [10.18.17.130]) by smtp.corp.redhat.com (Postfix) with ESMTP id D8CD96012C; Tue, 16 Jul 2019 14:57:15 +0000 (UTC) To: Kevin Wolf , Alexander Popov References: <1562335669-10127-1-git-send-email-alex.popov@linux.com> <0bce1e99-fb98-6354-9426-391a3e9363f1@linux.com> <20190716112535.GB7297@linux.fritz.box> From: John Snow Openpgp: preference=signencrypt Autocrypt: addr=jsnow@redhat.com; prefer-encrypt=mutual; keydata= mQINBFTKefwBEAChvwqYC6saTzawbih87LqBYq0d5A8jXYXaiFMV/EvMSDqqY4EY6whXliNO IYzhgrPEe7ZmPxbCSe4iMykjhwMh5byIHDoPGDU+FsQty2KXuoxto+ZdrP9gymAgmyqdk3aV vzzmCa3cOppcqKvA0Kqr10UeX/z4OMVV390V+DVWUvzXpda45/Sxup57pk+hyY52wxxjIqef rj8u5BN93s5uCVTus0oiVA6W+iXYzTvVDStMFVqnTxSxlpZoH5RGKvmoWV3uutByQyBPHW2U 1Y6n6iEZ9MlP3hcDqlo0S8jeP03HaD4gOqCuqLceWF5+2WyHzNfylpNMFVi+Hp0H/nSDtCvQ 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X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: sstabellini@kernel.org, pmatouse@redhat.com, mdroth@linux.vnet.ibm.com, qemu-block@nongnu.org, mst@redhat.com, qemu-devel@nongnu.org, qemu-stable@nongnu.org, pjp@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/16/19 7:25 AM, Kevin Wolf wrote: > Am 15.07.2019 um 13:24 hat Alexander Popov geschrieben: >> On 05.07.2019 17:07, Alexander Popov wrote: >>> This assertion was introduced in the commit a718978ed58a in July 2015. >>> It implies that the size of successful DMA transfers handled in >>> ide_dma_cb() should be multiple of 512 (the size of a sector). >>> >>> But guest systems can initiate DMA transfers that don't fit this >>> requirement. Let's improve the assertion to prevent qemu DoS from quests. >> >> Hello! >> >> Just a friendly ping. >> >> Could you have a look at this patch? > > John, I think this is for you. > > I haven't reviewed this yet, but if we put an assertion there that the > request is aligned, we probably rely on this fact somewhere in the code. > So I suspect that just changing the assertion without changing other > code, too, might not be enough. > > Kevin > Right; I'm aware of the patch. It's on the list to investigate today. I have the same concern that the assertion intuits a bug elsewhere, so I wanted to give this one a thorough investigation before inclusion for rc1. Sorry for the delay, it IS on my list, but I also feel that a privileged DOS by a guest of a legacy device is actually low priority security-wise, unless we can demonstrate that there are side effects that can be exploited. --js