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SubjectRe: [PATCH] nvme-pci: Avoid leak if pci_p2pmem_virt_to_bus() returns null
On Tue, Jun 25, 2019 at 12:09 AM Christoph Hellwig <hch@lst.de> wrote:
>
> On Mon, Jun 24, 2019 at 04:57:22PM -0700, Alan Mikhak wrote:
> > Modify nvme_alloc_sq_cmds() to call pci_free_p2pmem()
> > to free the memory it allocated using pci_alloc_p2pmem()
> > in case pci_p2pmem_virt_to_bus() returns null.
> >
> > Make sure not to call pci_free_p2pmem() if pci_alloc_p2pmem()
> > returned null which can happen if CONFIG_PCI_P2PDMA is not
> > configured.
>
> Can you
>

I mean this patch makes sure not to call pci_free_p2pmem() if nothing
was allocated by pci_alloc_p2pmem().

> >
> > Signed-off-by: Alan Mikhak <alan.mikhak@sifive.com>
> > ---
> > drivers/nvme/host/pci.c | 14 +++++++++-----
> > 1 file changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> > index 524d6bd6d095..5dfa067f6506 100644
> > --- a/drivers/nvme/host/pci.c
> > +++ b/drivers/nvme/host/pci.c
> > @@ -1456,11 +1456,15 @@ static int nvme_alloc_sq_cmds(struct nvme_dev *dev, struct nvme_queue *nvmeq,
> >
> > if (qid && dev->cmb_use_sqes && (dev->cmbsz & NVME_CMBSZ_SQS)) {
> > nvmeq->sq_cmds = pci_alloc_p2pmem(pdev, SQ_SIZE(depth));
> > - nvmeq->sq_dma_addr = pci_p2pmem_virt_to_bus(pdev,
> > - nvmeq->sq_cmds);
> > - if (nvmeq->sq_dma_addr) {
> > - set_bit(NVMEQ_SQ_CMB, &nvmeq->flags);
> > - return 0;
> > + if (nvmeq->sq_cmds) {
> > + nvmeq->sq_dma_addr = pci_p2pmem_virt_to_bus(pdev,
> > + nvmeq->sq_cmds);
> > + if (nvmeq->sq_dma_addr) {
> > + set_bit(NVMEQ_SQ_CMB, &nvmeq->flags);
> > + return 0;
> > + }
> > +
> > + pci_free_p2pmem(pdev, nvmeq->sq_cmds, SQ_SIZE(depth));
>
> pci_p2pmem_virt_to_bus should only fail when
> pci_p2pmem_virt_to_bus failed. That being said I think doing the
> error check on pci_alloc_p2pmem instead of relying on
> pci_p2pmem_virt_to_bus "passing through" the error seems odd, I'd
> rather check the pci_alloc_p2pmem return value directly.

Thanks Christoph. I could see the existing code should not leak but only after
inspecting pci_p2pmem_virt_to_bus() and gen_pool_virt_to_phys(). I wondered
what if these functions changed and broke the relation but that seems unlikely.
Checking the return value directly may require less from the reader,
if that's a good
outcome.

Alan

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