In vhost_iotlb_add_range_ctx(), validate the range size is non-zero before proceeding with adding it to the iotlb. Range size can overflow to 0 when start is 0 and last is (2^64 - 1). One instance where it can happen is when userspace sends an IOTLB message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an entry with size = 0, start = 0, last = (2^64 - 1) ends up in the iotlb. Next time a packet is sent, iotlb_access_ok() loops indefinitely due to that erroneous entry: Call Trace: <TASK> iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340 vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366 vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104 vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372 kthread+0x2e9/0x3a0 kernel/kthread.c:377 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK> Reported by syzbot at: https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87 Reported-by: syzbot+0abd373e2e50d704db87@xxxxxxxxxxxxxxxxxxxxxxxxx Tested-by: syzbot+0abd373e2e50d704db87@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Anirudh Rayabharam <mail@xxxxxxxxxxxxx> --- drivers/vhost/iotlb.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/vhost/iotlb.c b/drivers/vhost/iotlb.c index 670d56c879e5..b9de74bd2f9c 100644 --- a/drivers/vhost/iotlb.c +++ b/drivers/vhost/iotlb.c @@ -53,8 +53,10 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb, void *opaque) { struct vhost_iotlb_map *map; + u64 size = last - start + 1; - if (last < start) + // size can overflow to 0 when start is 0 and last is (2^64 - 1). + if (last < start || size == 0) return -EFAULT; if (iotlb->limit && @@ -69,7 +71,7 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb, return -ENOMEM; map->start = start; - map->size = last - start + 1; + map->size = size; map->last = last; map->addr = addr; map->perm = perm; -- 2.35.1
