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[87.11.6.2]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4548ec6b071sm2967434f8f.14.2026.05.08.02.26.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 May 2026 02:26:40 -0700 (PDT) Date: Fri, 8 May 2026 11:26:38 +0200 From: Stefano Garzarella To: Jakub Kicinski Cc: Eric Dumazet , "Michael S. Tsirkin" , Arseniy Krasnov , Bobby Eshleman , Stefan Hajnoczi , "David S . Miller" , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, eric.dumazet@gmail.com, Arseniy Krasnov , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , kvm@vger.kernel.org, virtualization@lists.linux.dev Subject: Re: [PATCH net] vsock/virtio: fix potential unbounded skb queue Message-ID: References: <20260506113554-mutt-send-email-mst@kernel.org> <20260507074113-mutt-send-email-mst@kernel.org> <20260507073340.0604667d@kernel.org> <20260507101805.6c3335d0@kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260507101805.6c3335d0@kernel.org> On Thu, May 07, 2026 at 10:18:05AM -0700, Jakub Kicinski wrote: >On Thu, 7 May 2026 09:32:24 -0700 Eric Dumazet wrote: >> On Thu, May 7, 2026 at 9:05 AM Stefano Garzarella wrote: >> > On Thu, May 07, 2026 at 07:33:40AM -0700, Jakub Kicinski wrote: >> > >We can revert if you think that the risk of regression is high.. >> > >Please LMK soon, we can do it before patch reaches Linus. >> > >> > Some tests in tools/testing/vsock/vsock_test.c are failing with this >> > patch applied. >> > >> > Test 18 are failing sometime in this way (I guess because we are >> > dropping packets): >> > >> > 18 - SOCK_STREAM MSG_ZEROCOPY...hash mismatch >> > >> > Test 22 is failing 100% in this way: >> > >> > 22 - SOCK_STREAM virtio credit update + SO_RCVLOWAT...send failed: >> > Resource temporarily unavailable >> > >> > >> > With my followup patch adding also advertisement to the other peer >> > (still draft locally, waiting for Michael proposal) I saw 22 failing, >> > because tests expects that can use the entire buf_alloc, but now we are >> > reducing it. So IMO we should do like in `__sock_set_rcvbuf()` and >> > double the buffer size, or at least digest an overhead equal to the >> > buffer size set by the user via SO_VM_SOCKETS_BUFFER_SIZE (yeah, >> > AF_VSOCK has it owns sockopt since the beginning :-(). >> > >> > With that approach tests are passing, but I'd like to stress a bit more >> > that patch. I'll send it tomorrow as fixup of this patch, or if you >> > prefer to revert, I'll send as standalone. >> >> A plain revert is a big issue, now users now how to crash hypervisors. >> >> This vulnerability allows a compromised guest (controlling >> virtio_vsock_hdr fields) >> to continuously flood the host's vsock receive queue without >> triggering any memory >> accounting limits or reader wakeups, resulting in unbounded host >> kernel memory consumption (Host DoS via OOM). >> >> A vulnerability where a KVM guest can crash or deadlock its host is >> classified as a KVM DoS. >> >> Am I missing something? > >Alright, let's leave it. > I posted a potential fixup: https://lore.kernel.org/netdev/20260508092330.69690-1-sgarzare@redhat.com/ Thanks, Stefano