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Tue, 02 Jun 2020 09:39:30 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id E0BDBC4339C; Tue, 2 Jun 2020 09:39:29 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: guptap) by smtp.codeaurora.org (Postfix) with ESMTPSA id 22DF2C433CA; Tue, 2 Jun 2020 09:39:29 +0000 (UTC) MIME-Version: 1.0 Date: Tue, 02 Jun 2020 15:09:29 +0530 From: guptap@codeaurora.org To: Robin Murphy Subject: Re: [PATCH] iommu/dma: limit iova free size to unmmaped iova In-Reply-To: <4ba082d3bb965524157704ea1ffb1ff4@codeaurora.org> References: <20200521113004.12438-1-guptap@codeaurora.org> <7aaa8dcc-6a47-f256-431d-2a1b034b4076@arm.com> <90662ef3123dbf2e93f9718ee5cc14a7@codeaurora.org> <2d873ab9-ebb9-3c2d-f129-55a036ab47d0@arm.com> <4ba082d3bb965524157704ea1ffb1ff4@codeaurora.org> Message-ID: <2bfb4ce3a2dfeb2d585f0308a9002feb@codeaurora.org> X-Sender: guptap@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Cc: mhocko@suse.com, owner-linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Andrew Morton X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: base64 Content-Type: text/plain; charset="utf-8"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" T24gMjAyMC0wNS0yNiAxMjo0OSwgZ3VwdGFwQGNvZGVhdXJvcmEub3JnIHdyb3RlOgo+IE9uIDIw MjAtMDUtMjIgMTQ6NTQsIFJvYmluIE11cnBoeSB3cm90ZToKPj4gT24gMjAyMC0wNS0yMiAwNzoy NSwgZ3VwdGFwQGNvZGVhdXJvcmEub3JnIHdyb3RlOgo+Pj4gT24gMjAyMC0wNS0yMiAwMTo0Niwg Um9iaW4gTXVycGh5IHdyb3RlOgo+Pj4+IE9uIDIwMjAtMDUtMjEgMTI6MzAsIFByYWthc2ggR3Vw dGEgd3JvdGU6Cj4+PiBJIGFncmVlLCB3ZSBzaG91bGRuJ3QgYmUgZnJlZWluZyB0aGUgcGFydGlh bCBpb3ZhLiBJbnN0ZWFkIGp1c3QgCj4+PiBtYWtpbmcKPj4+IHN1cmUgaWYgdW5tYXAgd2FzIHN1 Y2Nlc3NmdWwgc2hvdWxkIGJlIHN1ZmZpY2llbnQgYmVmb3JlIGZyZWVpbmcgCj4+PiBpb3ZhLiBT byBjaGFuZ2UKPj4+IGNhbiBpbnN0ZWFkIGJlIHNvbWV0aGluZyBsaWtlIHRoaXM6Cj4+PiAKPj4+ IC3CoMKgwqAgaW9tbXVfZG1hX2ZyZWVfaW92YShjb29raWUsIGRtYV9hZGRyLCBzaXplKTsKPj4+ ICvCoMKgwqAgaWYgKHVubWFwcGVkKQo+Pj4gK8KgwqDCoMKgwqDCoMKgIGlvbW11X2RtYV9mcmVl X2lvdmEoY29va2llLCBkbWFfYWRkciwgc2l6ZSk7Cj4+PiAKPj4+PiBUQkggbXkgZ3V0IGZlZWxp bmcgaGVyZSBpcyB0aGF0IHlvdSdyZSByZWFsbHkganVzdCB0cnlpbmcgdG8gdHJlYXQgYQo+Pj4+ IHN5bXB0b20gb2YgYW5vdGhlciBidWcgZWxzZXdoZXJlLCBuYW1lbHkgc29tZSBkcml2ZXIgY2Fs bGluZwo+Pj4+IGRtYV91bm1hcF8qIG9yIGRtYV9mcmVlXyogd2l0aCB0aGUgd3JvbmcgYWRkcmVz cyBvciBzaXplIGluIHRoZSAKPj4+PiBmaXJzdAo+Pj4+IHBsYWNlLgo+Pj4+IAo+Pj4gVGhpcyBj b25kaXRpb24gd291bGQgYXJpc2Ugb25seSBpZiBkcml2ZXIgY2FsbGluZyBkbWFfdW5tYXAvZnJl ZV8qIAo+Pj4gd2l0aCAwCj4+PiBpb3ZhX3Bmbi4gVGhpcyB3aWxsIGJlIGZsYWdnZWQgd2l0aCBh IHdhcm5pbmcgZHVyaW5nIHVubWFwIGJ1dCB3aWxsIAo+Pj4gdHJpZ2dlcgo+Pj4gcGFuaWMgbGF0 ZXIgb24gd2hpbGUgZG9pbmcgdW5yZWxhdGVkIGRtYV9tYXAvdW5tYXBfKi4gSWYgdW5tYXBwZWQg aGFzIAo+Pj4gYWxyZWFkeQo+Pj4gZmFpbGVkIGZvciBpbnZhbGlkIGlvdmEsIHRoZXJlIGlzIG5v IHJlYXNvbiB3ZSBzaG91bGQgY29uc2lkZXIgdGhpcyAKPj4+IGFzIHZhbGlkCj4+PiBpb3ZhIGFu ZCBmcmVlLiBUaGlzIHBhcnQgc2hvdWxkIGJlIGZpeGVkLgo+PiAKPj4gSSBkaXNhZ3JlZS4gSW4g Z2VuZXJhbCwgaWYgZHJpdmVycyBjYWxsIHRoZSBETUEgQVBJIGluY29ycmVjdGx5IGl0IGlzCj4+ IGxpYWJsZSB0byBsZWFkIHRvIGRhdGEgbG9zcywgbWVtb3J5IGNvcnJ1cHRpb24sIGFuZCB2YXJp b3VzIG90aGVyCj4+IHVucGxlYXNhbnQgbWlzYmVoYXZpb3VyIC0gaXQgaXMgbm90IHRoZSBETUEg bGF5ZXIncyBqb2IgdG8gYXR0ZW1wdCB0bwo+PiBwYXBlciBvdmVyIGRyaXZlciBidWdzLgo+PiAK Pj4gVGhlcmUgKmlzKiBhbiBhcmd1bWVudCBmb3IgZG93bmdyYWRpbmcgdGhlIEJVR19PTigpIGlu Cj4+IGlvdmFfbWFnYXppbmVfZnJlZV9wZm5zKCkgdG8gYSBXQVJOX09OKCksIHNpbmNlIGZyYW5r bHkgaXQgaXNuJ3QgYQo+PiBzdWZmaWNpZW50bHkgc2VyaW91cyBjb25kaXRpb24gdG8ganVzdGlm eSBraWxsaW5nIHRoZSB3aG9sZSBtYWNoaW5lCj4+IGltbWVkaWF0ZWx5LCBidXQgTkFLIHRvIGJv ZGdpbmcgdGhlIGlvbW11LWRtYSBtaWQtbGF5ZXIgdG8gImZpeCIgdGhhdC4KPj4gQSBzZXJpb3Vz IGJ1ZyBhbHJlYWR5IGhhcHBlbmVkIGVsc2V3aGVyZSwgc28gdHJ5aW5nIHRvIGhpZGUgdGhlCj4+ IGZhbGxvdXQgcmVhbGx5IGRvZXNuJ3QgaGVscCBhbnlvbmUuCj4+IAo+IFNvcnJ5IGZvciBkZWxh eWVkIHJlc3BvbnNlLCBpdCB3YXMgYSBsb25nIHdlZWtlbmQuCj4gSSBhZ3JlZSB0aGF0IGludmFs aWQgRE1BIEFQSSBjYWxsIGNhbiByZXN1bHQgaW4gdW5leHBlY3RlZCBpc3N1ZXMgYW5kIAo+IGNs aWVudAo+IHNob3VsZCBmaXggaXQsIGJ1dCB0aGVuIHRoZSBwcmVzZW50IGJlaGF2aW9yIG1ha2Vz IGl0IGRpZmZpY3VsdCB0byAKPiBjYXRjaCBjYXNlcwo+IHdoZW4gZHJpdmVyIGlzIG1ha2luZyB3 cm9uZyBETUEgQVBJIGNhbGxzLiBXaGVuIGludmFsaWQgaW92YSBwZm4gaXMgCj4gcGFzc2VkIGl0 Cj4gZG9lc24ndCBmYWlsIHRoZW4gYW5kIHRoZXJlLCB0aG91Z2ggRE1BIGxheWVyIGlzIGF3YXJl IG9mIGlvdmEgYmVpbmcgCj4gaW52YWxpZC4gSXQKPiBmYWlscyBtdWNoIGFmdGVyIHRoYXQgaW4g dGhlIGNvbnRleHQgb2YgYW4gdmFsaWQgbWFwL3VubWFwLCB3aXRoIAo+IEJVR19PTigpLgo+IAo+ IERvd25ncmFkaW5nIEJVR19PTigpIHRvIFdBUk5fT04oKSBpbiBpb3ZhX21hZ2F6aW5lX2ZyZWVf cGZucygpIHdpbGwgbm90IAo+IGhlbHAKPiBtdWNoIGFzIGludmFsaWQgaW92YSB3aWxsIGNhdXNl IE5VTEwgcG9pbnRlciBkZXJlZmVyZW5jZS4KPiAKPiBJIHNlZSBubyByZWFzb24gd2h5IERNQSBs YXllciB3YW50cyB0byBmcmVlIGFuIGlvdmEgZm9yIHdoaWNoIHVubWFwcGVkIAo+IGZhaWxlZC4K PiBJTUhPIHF1ZXVpbmcgYW4gaW52YWxpZCBpb3ZhICh3aGljaCBhbHJlYWR5IGZhaWxlZCB1bm1h cCkgdG8gcmNhY2hlIAo+IHdoaWNoCj4gZXZlbnR1YWxseSBnb2luZyB0byBjcmFzaCB0aGUgc3lz dGVtIGxvb2tzIGxpa2UgaW9tbXUtZG1hIGxheWVyIGlzc3VlLgo+IAo+IFRoYW5rcywKPiBQcmFr YXNoCgpwaW5nPwpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f Xwppb21tdSBtYWlsaW5nIGxpc3QKaW9tbXVAbGlzdHMubGludXgtZm91bmRhdGlvbi5vcmcKaHR0 cHM6Ly9saXN0cy5saW51eGZvdW5kYXRpb24ub3JnL21haWxtYW4vbGlzdGluZm8vaW9tbXU= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EAF14C433DF for ; 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Tue, 02 Jun 2020 09:39:30 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 65E52C433CB; Tue, 2 Jun 2020 09:39:30 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: guptap) by smtp.codeaurora.org (Postfix) with ESMTPSA id 22DF2C433CA; Tue, 2 Jun 2020 09:39:29 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Date: Tue, 02 Jun 2020 15:09:29 +0530 From: guptap@codeaurora.org To: Robin Murphy Cc: Andrew Morton , mhocko@suse.com, joro@8bytes.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, owner-linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [PATCH] iommu/dma: limit iova free size to unmmaped iova In-Reply-To: <4ba082d3bb965524157704ea1ffb1ff4@codeaurora.org> References: <20200521113004.12438-1-guptap@codeaurora.org> <7aaa8dcc-6a47-f256-431d-2a1b034b4076@arm.com> <90662ef3123dbf2e93f9718ee5cc14a7@codeaurora.org> <2d873ab9-ebb9-3c2d-f129-55a036ab47d0@arm.com> <4ba082d3bb965524157704ea1ffb1ff4@codeaurora.org> Message-ID: <2bfb4ce3a2dfeb2d585f0308a9002feb@codeaurora.org> X-Sender: guptap@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 X-Rspamd-Queue-Id: 9B770989E X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2020-05-26 12:49, guptap@codeaurora.org wrote: > On 2020-05-22 14:54, Robin Murphy wrote: >> On 2020-05-22 07:25, guptap@codeaurora.org wrote: >>> On 2020-05-22 01:46, Robin Murphy wrote: >>>> On 2020-05-21 12:30, Prakash Gupta wrote: >>> I agree, we shouldn't be freeing the partial iova. Instead just=20 >>> making >>> sure if unmap was successful should be sufficient before freeing=20 >>> iova. So change >>> can instead be something like this: >>>=20 >>> -=C2=A0=C2=A0=C2=A0 iommu_dma_free_iova(cookie, dma_addr, size); >>> +=C2=A0=C2=A0=C2=A0 if (unmapped) >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 iommu_dma_free_iova(cooki= e, dma_addr, size); >>>=20 >>>> TBH my gut feeling here is that you're really just trying to treat a >>>> symptom of another bug elsewhere, namely some driver calling >>>> dma_unmap_* or dma_free_* with the wrong address or size in the=20 >>>> first >>>> place. >>>>=20 >>> This condition would arise only if driver calling dma_unmap/free_*=20 >>> with 0 >>> iova_pfn. This will be flagged with a warning during unmap but will=20 >>> trigger >>> panic later on while doing unrelated dma_map/unmap_*. If unmapped has= =20 >>> already >>> failed for invalid iova, there is no reason we should consider this=20 >>> as valid >>> iova and free. This part should be fixed. >>=20 >> I disagree. In general, if drivers call the DMA API incorrectly it is >> liable to lead to data loss, memory corruption, and various other >> unpleasant misbehaviour - it is not the DMA layer's job to attempt to >> paper over driver bugs. >>=20 >> There *is* an argument for downgrading the BUG_ON() in >> iova_magazine_free_pfns() to a WARN_ON(), since frankly it isn't a >> sufficiently serious condition to justify killing the whole machine >> immediately, but NAK to bodging the iommu-dma mid-layer to "fix" that. >> A serious bug already happened elsewhere, so trying to hide the >> fallout really doesn't help anyone. >>=20 > Sorry for delayed response, it was a long weekend. > I agree that invalid DMA API call can result in unexpected issues and=20 > client > should fix it, but then the present behavior makes it difficult to=20 > catch cases > when driver is making wrong DMA API calls. When invalid iova pfn is=20 > passed it > doesn't fail then and there, though DMA layer is aware of iova being=20 > invalid. It > fails much after that in the context of an valid map/unmap, with=20 > BUG_ON(). >=20 > Downgrading BUG_ON() to WARN_ON() in iova_magazine_free_pfns() will not= =20 > help > much as invalid iova will cause NULL pointer dereference. >=20 > I see no reason why DMA layer wants to free an iova for which unmapped=20 > failed. > IMHO queuing an invalid iova (which already failed unmap) to rcache=20 > which > eventually going to crash the system looks like iommu-dma layer issue. >=20 > Thanks, > Prakash ping?