linux-kernel - Re: [PATCH] PCI: endpoint: Fix use after free in pci_epf_remove

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Message-ID: <20211206114532.GB18520@lpieralisi>
Date:   Mon, 6 Dec 2021 11:45:32 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Shunsuke Mie <mie@...l.co.jp>, kishon@...com
Cc:     bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: endpoint: Fix use after free in pci_epf_remove_cfs()

[dropped stable, erroneously added to the CC list]

On Mon, Jun 21, 2021 at 04:00:58PM +0900, Shunsuke Mie wrote:
> All of entries are freed in a loop, however, the freed entry is accessed
> by list_del() after the loop.
> 
> When epf driver that includes pci-epf-test unload, the pci_epf_remove_cfs()
> is called, and occurred the use after free. Therefore, kernel panics
> randomly after or while the module unloading.
> 
> I tested this patch with r8a77951-Salvator-xs boards.
> 
> Fixes: ef1433f ("PCI: endpoint: Create configfs entry for each pci_epf_device_id table entry")
> Signed-off-by: Shunsuke Mie <mie@...l.co.jp>
> ---
>  drivers/pci/endpoint/pci-epf-core.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Kishon, please review this patch, thanks.

Lorenzo

> 
> diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
> index e9289d10f822..538e902b0ba6 100644
> --- a/drivers/pci/endpoint/pci-epf-core.c
> +++ b/drivers/pci/endpoint/pci-epf-core.c
> @@ -202,8 +202,10 @@ static void pci_epf_remove_cfs(struct pci_epf_driver *driver)
>  		return;
>  
>  	mutex_lock(&pci_epf_mutex);
> -	list_for_each_entry_safe(group, tmp, &driver->epf_group, group_entry)
> +	list_for_each_entry_safe(group, tmp, &driver->epf_group, group_entry) {
> +		list_del(&group->group_entry);
>  		pci_ep_cfs_remove_epf_group(group);
> +	}
>  	list_del(&driver->epf_group);
>  	mutex_unlock(&pci_epf_mutex);
>  }
> -- 
> 2.17.1
>