Hi Anant, > When the amount of data stored in the location corresponding to > iov_iter *from is less then 4, some data seems to go uninitialized. > > Updating this condition accordingly, makes sense both intuitively and > logically as well, since the other check for extreme condition done is if > len > HCI_MAX_FRAME_SIZE, which is HCI_MAX_ACL_SIZE (which is 1024) + 4; > which itself gives some idea about what must be the ideal mininum size. > > Reported-and-tested by: syzbot+4c14a8f574461e1c3659@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Anant Thazhemadam <anant.thazhemadam@xxxxxxxxx> > --- > If there is some explicit reason why len < 4 doesn't work, and only len < 2 works, > please do let me know. > The commit message that introduced the initial change > (512b2268156a4e15ebf897f9a883bdee153a54b7) wasn't exactly very helpful in this > respect, and I couldn't find a whole lot of discussion regarding this either. > > drivers/bluetooth/hci_vhci.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c > index 8ab26dec5f6e..0c49821d7b98 100644 > --- a/drivers/bluetooth/hci_vhci.c > +++ b/drivers/bluetooth/hci_vhci.c > @@ -159,7 +159,7 @@ static inline ssize_t vhci_get_user(struct vhci_data *data, > __u8 pkt_type, opcode; > int ret; > > - if (len < 2 || len > HCI_MAX_FRAME_SIZE) > + if (len < 4 || len > HCI_MAX_FRAME_SIZE) > return -EINVAL; so the minimum requirement is to have an 1 octet packet indicator. If some other functions are missing length checks, then it should be fixed there. I see that in case of HCI_VENDOR_PKT we need to check for the 2nd octet to be present, but I have no idea why you require 3 octets minimum. As I said, if so, then the other functions that get called require proper range checks. Regards Marcel
