On Tue, Feb 22, 2022 at 01:23:03AM +0530, Anirudh Rayabharam wrote: > 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). Pls use the old-style /* */ comments. > + 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
