On Tue, Feb 22, 2022 at 10:50:20AM +0800, Jason Wang wrote: > On Tue, Feb 22, 2022 at 3:53 AM Anirudh Rayabharam <mail@xxxxxxxxxxxxx> 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). > > + if (last < start || size == 0) > > return -EFAULT; > > I'd move this check to vhost_chr_iter_write(), then for the device who > has its own msg handler (e.g vDPA) can benefit from it as well. Thanks for reviewing! I kept the check here thinking that all devices would benefit from it because they would need to call vhost_iotlb_add_range() to add an entry to the iotlb. Isn't that correct? Do you see any other benefit in moving it to vhost_chr_iter_write()? One concern I have is that if we move it out some future caller to vhost_iotlb_add_range() might forget to handle this case. Thanks! - Anirudh. > > Thanks > > > > > 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 > > >
