2021-03-26 09:39:16

by Shradha Todi

Subject: [PATCH v5] PCI: endpoint: Fix NULL pointer dereference for ->get_features()

get_features ops of pci_epc_ops may return NULL, causing NULL pointer
dereference in pci_epf_test_alloc_space function. Let us add a check for
pci_epc_feature pointer in pci_epf_test_bind before we access it to avoid
any such NULL pointer dereference and return -ENOTSUPP in case
pci_epc_feature is not found.

When the patch is not applied and EPC features is not implemented in the
platform driver, we see the following dump due to kernel NULL pointer
dereference.

Call trace:
pci_epf_test_bind+0xf4/0x388
pci_epf_bind+0x3c/0x80
pci_epc_epf_link+0xa8/0xcc
configfs_symlink+0x1a4/0x48c
vfs_symlink+0x104/0x184
do_symlinkat+0x80/0xd4
__arm64_sys_symlinkat+0x1c/0x24
el0_svc_common.constprop.3+0xb8/0x170
el0_svc_handler+0x70/0x88
el0_svc+0x8/0x640
Code: d2800581 b9403ab9 f9404ebb 8b394f60 (f9400400)
---[ end trace a438e3c5a24f9df0 ]---

Fixes: 2c04c5b8eef79 ("PCI: pci-epf-test: Use pci_epc_get_features() to get EPC features")
Reviewed-by: Pankaj Dubey <[email protected]>
Reviewed-by: Kishon Vijay Abraham I <[email protected]>
Signed-off-by: Sriram Dash <[email protected]>
Signed-off-by: Shradha Todi <[email protected]>
---
Changes w.r.t. v4:
https://lkml.org/lkml/2021/1/12/815
- Changed commit message to remove time stamp as suggested by Lorenzo
- Since deference in not actually happening in bind function, mentioned
the same in the commit message as suggested by Leon.

drivers/pci/endpoint/functions/pci-epf-test.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index c0ac4e9cbe72..bc35b3566be6 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -833,15 +833,18 @@ static int pci_epf_test_bind(struct pci_epf *epf)
return -EINVAL;

epc_features = pci_epc_get_features(epc, epf->func_no);
- if (epc_features) {
- linkup_notifier = epc_features->linkup_notifier;
- core_init_notifier = epc_features->core_init_notifier;
- test_reg_bar = pci_epc_get_first_free_bar(epc_features);
- if (test_reg_bar < 0)
- return -EINVAL;
- pci_epf_configure_bar(epf, epc_features);
+ if (!epc_features) {
+ dev_err(&epf->dev, "epc_features not implemented\n");
+ return -EOPNOTSUPP;
}

+ linkup_notifier = epc_features->linkup_notifier;
+ core_init_notifier = epc_features->core_init_notifier;
+ test_reg_bar = pci_epc_get_first_free_bar(epc_features);
+ if (test_reg_bar < 0)
+ return -EINVAL;
+ pci_epf_configure_bar(epf, epc_features);
+
epf_test->test_reg_bar = test_reg_bar;
epf_test->epc_features = epc_features;

--
2.17.1

2021-03-26 15:27:05

by Lorenzo Pieralisi

Subject: Re: [PATCH v5] PCI: endpoint: Fix NULL pointer dereference for ->get_features()

On Wed, 24 Mar 2021 15:46:09 +0530, Shradha Todi wrote:
> get_features ops of pci_epc_ops may return NULL, causing NULL pointer
> dereference in pci_epf_test_alloc_space function. Let us add a check for
> pci_epc_feature pointer in pci_epf_test_bind before we access it to avoid
> any such NULL pointer dereference and return -ENOTSUPP in case
> pci_epc_feature is not found.
>
> When the patch is not applied and EPC features is not implemented in the
> platform driver, we see the following dump due to kernel NULL pointer
> dereference.
>
> [...]

Applied to pci/endpoint, thanks!

[1/1] PCI: endpoint: Fix NULL pointer dereference for ->get_features()
https://git.kernel.org/lpieralisi/pci/c/6613bc2301

Thanks,
Lorenzo