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[2a02:a463:a071:0:8f3f:3afb:28f6:19c0]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-69cd26e239esm3355874a12.0.2026.07.15.09.41.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jul 2026 09:41:43 -0700 (PDT) From: Hari Mishal To: David Hildenbrand , "Michael S . Tsirkin" , Jason Wang Cc: Greg Kroah-Hartman , Xuan Zhuo , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, Hari Mishal Subject: [PATCH v2 1/4] virtio-mem: validate device-reported block size Date: Wed, 15 Jul 2026 18:41:16 +0200 Message-ID: <20260715164139.40957-1-harimishal1@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260715142337.22811-2-harimishal1@gmail.com> References: <20260715142337.22811-2-harimishal1@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 ram, post crash. Reject both at init time instead of trusting the device. Signed-off-by: Hari Mishal --- v2: dropped the redundant explicit zero check, since is_power_of_2(0) already returns false. drivers/virtio/virtio_mem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 11c441501582..0e04fec458af 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -2847,6 +2847,12 @@ 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 (!is_power_of_2(vm->device_block_size)) { + 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