| Message ID | 20211118070202.2739158-1-jordy@pwning.systems (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v2] nfc: st-nci: Fix potential buffer overflows in EVT_TRANSACTION | expand |
On 18/11/2021 08:02, Jordy Zomer wrote: > It appears that there are some buffer overflows in EVT_TRANSACTION. > This happens because the length parameters that are passed to memcpy > come directly from skb->data and are not guarded in any way. > > It would be nice if someone can review and test this patch because > I don't own the hardware :) Thanks for your patch. You mentioned that there are buffer overflows but you do not own the hardware. How do you know these overflow exist? How did you detect them? > > EDIT: Changed comment style and double newlines Please add changelog after --- separators so it does not clutter the commit log with unrelated "EDIT". > > Signed-off-by: Jordy Zomer <jordy@pwning.systems> > --- > drivers/nfc/st-nci/se.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/drivers/nfc/st-nci/se.c b/drivers/nfc/st-nci/se.c > index 7764b1a4c3cf..8e2ac8a3d199 100644 > --- a/drivers/nfc/st-nci/se.c > +++ b/drivers/nfc/st-nci/se.c > @@ -335,6 +335,11 @@ static int st_nci_hci_connectivity_event_received(struct nci_dev *ndev, > return -ENOMEM; > > transaction->aid_len = skb->data[1]; > + > + /* Checking if the length of the AID is valid */ > + if (transaction->aid_len > sizeof(transaction->aid)) > + return -EINVAL; I am thinking whether the check should be before memory allocation - to save on useless memory allocation in case of error, but make the code less obvious with referring to skb->data[1] twice. > + > memcpy(transaction->aid, &skb->data[2], transaction->aid_len); > > /* Check next byte is PARAMETERS tag (82) */ > @@ -343,6 +348,16 @@ static int st_nci_hci_connectivity_event_received(struct nci_dev *ndev, > return -EPROTO; > > transaction->params_len = skb->data[transaction->aid_len + 3]; > + > + /* > + * check if the length of the parameters is valid > + * we can't use sizeof(transaction->params) because it's > + * a flexible array member so we have to check if params_len > + * is bigger than the space allocated for the array > + */ > + if (transaction->params_len > ((skb->len - 2) - sizeof(struct nfc_evt_transaction))) > + return -EINVAL; The current comment is long and actually not explaining how you get "-2" and sizeof, so how about: "Total size is allocated (skb->len - 2) minus fixed array members)" In general the code looks ok, although I cannot provide tests. > + > memcpy(transaction->params, skb->data + > transaction->aid_len + 4, transaction->params_len); > > Best regards, Krzysztof
diff --git a/drivers/nfc/st-nci/se.c b/drivers/nfc/st-nci/se.c index 7764b1a4c3cf..8e2ac8a3d199 100644 --- a/drivers/nfc/st-nci/se.c +++ b/drivers/nfc/st-nci/se.c @@ -335,6 +335,11 @@ static int st_nci_hci_connectivity_event_received(struct nci_dev *ndev, return -ENOMEM; transaction->aid_len = skb->data[1]; + + /* Checking if the length of the AID is valid */ + if (transaction->aid_len > sizeof(transaction->aid)) + return -EINVAL; + memcpy(transaction->aid, &skb->data[2], transaction->aid_len); /* Check next byte is PARAMETERS tag (82) */ @@ -343,6 +348,16 @@ static int st_nci_hci_connectivity_event_received(struct nci_dev *ndev, return -EPROTO; transaction->params_len = skb->data[transaction->aid_len + 3]; + + /* + * check if the length of the parameters is valid + * we can't use sizeof(transaction->params) because it's + * a flexible array member so we have to check if params_len + * is bigger than the space allocated for the array + */ + if (transaction->params_len > ((skb->len - 2) - sizeof(struct nfc_evt_transaction))) + return -EINVAL; + memcpy(transaction->params, skb->data + transaction->aid_len + 4, transaction->params_len);
It appears that there are some buffer overflows in EVT_TRANSACTION. This happens because the length parameters that are passed to memcpy come directly from skb->data and are not guarded in any way. It would be nice if someone can review and test this patch because I don't own the hardware :) EDIT: Changed comment style and double newlines Signed-off-by: Jordy Zomer <jordy@pwning.systems> --- drivers/nfc/st-nci/se.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)