[Linux-kernel-mentees] [PATCH] Fix uninit-value in hci_chan_lookup_handle
marcel at holtmann.org
Sat Sep 26 07:46:49 UTC 2020
> 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 at syzkaller.appspotmail.com
> Signed-off-by: Anant Thazhemadam <anant.thazhemadam at gmail.com>
> 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.
More information about the Linux-kernel-mentees