Re: [PATCH] PCI: endpoint: pci-epf-test: Make use of cached 'epc_features' in pci_epf_test_core_init()

Niklas Cassel
2024-04-17T17:49:50Z

On Wed, Apr 17, 2024 at 10:47:25PM +0530, Manivannan Sadhasivam wrote:
> Instead of getting the epc_features from pci_epc_get_features() API, use
> the cached pci_epf_test::epc_features value to avoid the NULL check. Since
> the NULL check is already performed in pci_epf_test_bind(), having one more
> check in pci_epf_test_core_init() is redundant and it is not possible to
> hit the NULL pointer dereference. This also leads to the following smatch
> warning:
>
> drivers/pci/endpoint/functions/pci-epf-test.c:784 pci_epf_test_core_init()
> error: we previously assumed 'epc_features' could be null (see line 747)
>
> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> Closes: https://lore.kernel.org/linux-pci/024b5826-7180-4076-ae08-57d2584cca3f@moroto.mountain/
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

I think you forgot:
Fixes: a01e7214bef9 ("PCI: endpoint: Remove "core_init_notifier" flag")

> ---
> drivers/pci/endpoint/functions/pci-epf-test.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 977fb79c1567..0d28f413cb07 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -743,11 +743,10 @@ static int pci_epf_test_core_init(struct pci_epf *epf)
> bool msi_capable = true;
> int ret;
>
> - epc_features = pci_epc_get_features(epc, epf->func_no, epf->vfunc_no);
> - if (epc_features) {
> - msix_capable = epc_features->msix_capable;
> - msi_capable = epc_features->msi_capable;
> - }
> + epc_features = epf_test->epc_features;

How about:

index 977fb79c1567..4d6105c07ac0 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -735,7 +735,7 @@ static int pci_epf_test_core_init(struct pci_epf *epf)
{
struct pci_epf_test *epf_test = epf_get_drvdata(epf);
struct pci_epf_header *header = epf->header;
- const struct pci_epc_features *epc_features;
+ const struct pci_epc_features *epc_features = epf_test->epc_features;
struct pci_epc *epc = epf->epc;
struct device *dev = &epf->dev;
bool linkup_notifier = false;
@@ -743,12 +743,6 @@ static int pci_epf_test_core_init(struct pci_epf *epf)
bool msi_capable = true;
int ret;

- epc_features = pci_epc_get_features(epc, epf->func_no, epf->vfunc_no);
- if (epc_features) {
- msix_capable = epc_features->msix_capable;
- msi_capable = epc_features->msi_capable;
- }
-
if (epf->vfunc_no <= 1) {
ret = pci_epc_write_header(epc, epf->func_no, epf->vfunc_no, header);
if (ret) {
@@ -761,6 +755,7 @@ static int pci_epf_test_core_init(struct pci_epf *epf)
if (ret)
return ret;

+ msi_capable = epc_features->msi_capable;
if (msi_capable) {
ret = pci_epc_set_msi(epc, epf->func_no, epf->vfunc_no,
epf->msi_interrupts);
@@ -770,6 +765,7 @@ static int pci_epf_test_core_init(struct pci_epf *epf)
}
}

+ msix_capable = epc_features->msix_capable;
if (msix_capable) {
ret = pci_epc_set_msix(epc, epf->func_no, epf->vfunc_no,
epf->msix_interrupts,
@@ -814,11 +810,9 @@ static int pci_epf_test_alloc_space(struct pci_epf *epf)
void *base;
enum pci_barno test_reg_bar = epf_test->test_reg_bar;
enum pci_barno bar;
- const struct pci_epc_features *epc_features;
+ const struct pci_epc_features *epc_features = epf_test->epc_features;
size_t test_reg_size;

- epc_features = epf_test->epc_features;
-
test_reg_bar_size = ALIGN(sizeof(struct pci_epf_test_reg), 128);

msix_capable = epc_features->msix_capable;

Instead?

That way, we assign msi_capable/msix_capable just before the if-statement
where it is used. (Which matches how we already assign msix_capable just
before the if-statement in pci_epf_test_alloc_space().)

Kind regards,
Niklas

> +
> + msix_capable = epc_features->msix_capable;
> + msi_capable = epc_features->msi_capable;
>
> if (epf->vfunc_no <= 1) {
> ret = pci_epc_write_header(epc, epf->func_no, epf->vfunc_no, header);
>
> ---
> base-commit: 6e47dcb2ca223211c43c37497836cd9666c70674
> change-id: 20240417-pci-epf-test-fix-2209ae22be80
>
> Best regards,
> --
> Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
>