[net-qed] question about potential null pointer dereference

[net-qed] question about potential null pointer dereference

[Gustavo A. R. Silva]

Hello everybody,

While looking into Coverity ID 1362293 I ran into the following piece  
of code at drivers/net/ethernet/qlogic/qed/qed_sriov.c:3863:

3863static int
3864qed_iov_configure_min_tx_rate(struct qed_dev *cdev, int vfid, u32 rate)
3865{
3866        struct qed_vf_info *vf;
3867        u8 vport_id;
3868        int i;
3869
3870        for_each_hwfn(cdev, i) {
3871                struct qed_hwfn *p_hwfn = &cdev->hwfns[i];
3872
3873                if (!qed_iov_pf_sanity_check(p_hwfn, vfid)) {
3874                        DP_NOTICE(p_hwfn,
3875                                  "SR-IOV sanity check failed,  
can't set min rate\n");
3876                        return -EINVAL;
3877                }
3878        }
3879
3880        vf = qed_iov_get_vf_info(QED_LEADING_HWFN(cdev), (u16)vfid, true);
3881        vport_id = vf->vport_id;
3882
3883        return qed_configure_vport_wfq(cdev, vport_id, rate);
3884}

The issue here is that in case function qed_iov_get_vf_info() at line  
3880, returns NULL, a NULL pointer dereference will take place at line  
3881.

Maybe a patch like the following could be applied in order to avoid  
any potential NULL pointer dereference:

index 71e392f..6bf1f0e2 100644
--- a/drivers/net/ethernet/qlogic/qed/qed_sriov.c
+++ b/drivers/net/ethernet/qlogic/qed/qed_sriov.c
@@ -3878,6 +3878,9 @@ qed_iov_configure_min_tx_rate(struct qed_dev  
*cdev, int vfid, u32 rate)
         }

         vf = qed_iov_get_vf_info(QED_LEADING_HWFN(cdev), (u16)vfid, true);
+       if (!vf)
+               return -EINVAL;
+
         vport_id = vf->vport_id;

         return qed_configure_vport_wfq(cdev, vport_id, rate);


What do you think?

I'd really appreciate any comment on this.

Thank you!
--
Gustavo A. R. Silva

RE: [net-qed] question about potential null pointer dereference

[Mintz, Yuval]

> While looking into Coverity ID 1362293 I ran into the following piece of code
> at drivers/net/ethernet/qlogic/qed/qed_sriov.c:3863:
> 
> 3863static int
> 3864qed_iov_configure_min_tx_rate(struct qed_dev *cdev, int vfid, u32 rate)
> 3865{
> 3866        struct qed_vf_info *vf;
> 3867        u8 vport_id;
> 3868        int i;
> 3869
> 3870        for_each_hwfn(cdev, i) {
> 3871                struct qed_hwfn *p_hwfn = &cdev->hwfns[i];
> 3872
> 3873                if (!qed_iov_pf_sanity_check(p_hwfn, vfid)) {
> 3874                        DP_NOTICE(p_hwfn,
> 3875                                  "SR-IOV sanity check failed,
> can't set min rate\n");
> 3876                        return -EINVAL;
> 3877                }
> 3878        }
> 3879
> 3880        vf = qed_iov_get_vf_info(QED_LEADING_HWFN(cdev), (u16)vfid,
> true);

Unless I'm missing something, this sounds like a false-positive from coverity.
The validation of qed_iov_pf_sanity_check() should be sufficient for qed_iov_get_vf_info()
to always return a valid value, and there's no scenario where we'd reach this
part of the code if the hw-functions aren't initialized; so we're bound to enter the loop.