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[2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37895676093sm14372086f8f.65.2024.09.12.06.36.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Sep 2024 06:36:33 -0700 (PDT) Date: Thu, 12 Sep 2024 15:36:32 +0200 From: Stefano Brivio To: Laurent Vivier Subject: Re: [PATCH v4 2/4] vhost-user: introduce virtio API Message-ID: <20240912153632.66e880b1@elisabeth> In-Reply-To: References: <20240906160455.2088854-1-lvivier@redhat.com> <20240906160455.2088854-3-lvivier@redhat.com> <20240910174731.3c4db56f@elisabeth> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: ZDM5TUEWBZXH7IBJ4CJNUEW523BHXY7X X-Message-ID-Hash: ZDM5TUEWBZXH7IBJ4CJNUEW523BHXY7X X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Thu, 12 Sep 2024 13:23:58 +0200 Laurent Vivier wrote: > On 10/09/2024 17:47, Stefano Brivio wrote: > >> + > >> +/** > >> + * virtqueue_read_indirect_desc() - Copy virtio ring descriptors from guest > >> + * memory > >> + * @dev: Vhost-user device > >> + * @desc: Destination address to copy the descriptors to > >> + * @addr: Guest memory address to copy from > >> + * @len: Length of memory to copy > >> + * > >> + * Return: -1 if there is an error, 0 otherwise > >> + */ > >> +static int virtqueue_read_indirect_desc(struct vu_dev *dev, struct vring_desc *desc, > >> + uint64_t addr, size_t len) > >> +{ > >> + uint64_t read_len; > >> + > >> + if (len > (VIRTQUEUE_MAX_SIZE * sizeof(struct vring_desc))) > >> + return -1; > >> + > >> + if (len == 0) > >> + return -1; > >> + > >> + while (len) { > >> + const struct vring_desc *orig_desc; > >> + > >> + read_len = len; > >> + orig_desc = vu_gpa_to_va(dev, &read_len, addr); > > In case you missed this in my review of v3 (I'm not sure if it's a > > valid concern): > > > > -- > > Should we also return if read_len < sizeof(struct vring_desc) after > > this call? Can that ever happen, if we pick a particular value of addr > > so that it's almost at the end of a region? > > -- > > In fact, read_len can be < sizeof(struct vring_desc) after this call but if orig_desc != > NULL it means we can continue in another region to continue to fill the structure. Right, I see that. > If there is not enough memory to fill "len" bytes it exits with -1. ...and this as well. But let's say that read_len is 1 (and struct vring_desc is 16 bytes). Then: memcpy(desc, orig_desc, read_len); copies one byte [...] desc += read_len / sizeof(struct vring_desc); doesn't increase desc. At the next iteration with len > 0 and read_len > 0, the memcpy() will overwrite that one byte, as we didn't increase desc. Or it's not possible for some other reason? -- Stefano