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[80.230.24.117]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49508731fcdsm140971355e9.4.2026.07.15.08.57.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jul 2026 08:57:05 -0700 (PDT) Date: Wed, 15 Jul 2026 11:57:01 -0400 From: "Michael S. Tsirkin" To: Hari Mishal Cc: Amit Shah , Arnd Bergmann , Greg Kroah-Hartman , Gerd Hoffmann , Jason Wang , David Hildenbrand , Henrik Rydberg , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, linux-input@vger.kernel.org Subject: Re: [PATCH 1/4] virtio-mem: validate device-reported block size Message-ID: <20260715115206-mutt-send-email-mst@kernel.org> References: <20260715142337.22811-1-harimishal1@gmail.com> <20260715142337.22811-2-harimishal1@gmail.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20260715142337.22811-2-harimishal1@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: KqtzJgVo7HUJn0P2i3W2BFvIJefsTPGj7-Yr0Wg52YE_1784131026 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Jul 15, 2026 at 04:22:40PM +0200, Hari Mishal wrote: > The device_block_size read from the virtio-mem config space is used > as a divisor and also in ALIGN_DOWN() further down the code path in > the driver without further validation. A zero value leads to a division > by zero, and a non-power-of-two value corrupts the ALIGN_DOWN() bitmask > arithmetic leading to a misreporting of guest usable guest ram, post > crash. Reject both at init time instead of trusting the device. > > Assisted-by: gkh_clanker:t1000 > Signed-off-by: Hari Mishal > --- > drivers/virtio/virtio_mem.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c > index 11c441501582..43d12ec7c323 100644 > --- a/drivers/virtio/virtio_mem.c > +++ b/drivers/virtio/virtio_mem.c > @@ -2847,6 +2847,13 @@ static int virtio_mem_init(struct virtio_mem *vm) > &vm->plugged_size); > virtio_cread_le(vm->vdev, struct virtio_mem_config, block_size, > &vm->device_block_size); > + if (!vm->device_block_size || > + !is_power_of_2(vm->device_block_size)) { 0 is not a power of 2, why do we need to check twice? > + dev_err(&vm->vdev->dev, > + "invalid device block size: 0x%llx\n", > + (unsigned long long)vm->device_block_size); > + return -EINVAL; > + } > virtio_cread_le(vm->vdev, struct virtio_mem_config, node_id, > &node_id); > vm->nid = virtio_mem_translate_node_id(vm, node_id); > -- > 2.43.0