linux-kernel - Re: [PATCH v3] PCI: endpoint: Fix NULL pointer dereference for ->get

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Message-ID: <20210106113951.GW31158@unreal>
Date:   Wed, 6 Jan 2021 13:39:51 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Shradha Todi <shradha.t@...sung.com>
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        bhelgaas@...gle.com, kishon@...com, lorenzo.pieralisi@....com,
        pankaj.dubey@...sung.com, sriram.dash@...sung.com,
        niyas.ahmed@...sung.com, p.rajanbabu@...sung.com,
        l.mehra@...sung.com, hari.tv@...sung.com
Subject: Re: [PATCH v3] PCI: endpoint: Fix NULL pointer dereference for
 ->get_features()

On Wed, Jan 06, 2021 at 04:08:10PM +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 ]---
>
> Fixes: 2c04c5b8eef79 ("PCI: pci-epf-test: Use pci_epc_get_features() to get
> EPC features")
>
> Reviewed-by: Pankaj Dubey <pankaj.dubey@...sung.com>

Please no space between Fixes line and SOB.
Also please don't break Fixes lines.

Thanks