Re: [PATCH v4] PCI: endpoint: Fix NULL pointer dereference for ->get_features()

Leon Romanovsky
2021-01-13T07:22:07Z

On Tue, Jan 12, 2021 at 07:32:25PM +0530, Shradha Todi wrote:
> get_features ops of pci_epc_ops may return NULL, causing NULL pointer
> dereference in pci_epf_test_bind 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.
>
> [ 105.135936] Call trace:
> [ 105.138363] pci_epf_test_bind+0xf4/0x388
> [ 105.142354] pci_epf_bind+0x3c/0x80
> [ 105.145817] pci_epc_epf_link+0xa8/0xcc
> [ 105.149632] configfs_symlink+0x1a4/0x48c
> [ 105.153616] vfs_symlink+0x104/0x184
> [ 105.157169] do_symlinkat+0x80/0xd4
> [ 105.160636] __arm64_sys_symlinkat+0x1c/0x24
> [ 105.164885] el0_svc_common.constprop.3+0xb8/0x170
> [ 105.169649] el0_svc_handler+0x70/0x88
> [ 105.173377] el0_svc+0x8/0x640
> [ 105.176411] Code: d2800581 b9403ab9 f9404ebb 8b394f60 (f9400400)
> [ 105.182478] ---[ end trace a438e3c5a24f9df0 ]---

Description and call trace don't correlate with the proposed code change.

The code in pci_epf_test_bind() doesn't dereference epc_features, at
least in direct manner.

Thanks