linux-hardening - Re: [PATCH] igbvf: replace deprecated strncpy with strscpy

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Date: Tue, 10 Oct 2023 14:33:49 -0700
From: Jesse Brandeburg <jesse.brandeburg@...el.com>
To: Justin Stitt <justinstitt@...gle.com>, Tony Nguyen
	<anthony.l.nguyen@...el.com>, "David S. Miller" <davem@...emloft.net>, "Eric
 Dumazet" <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>
CC: <intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-hardening@...r.kernel.org>
Subject: Re: [PATCH] igbvf: replace deprecated strncpy with strscpy

On 10/10/2023 2:20 PM, Jesse Brandeburg wrote:
> On 10/10/2023 2:12 PM, Justin Stitt wrote:
>> `strncpy` is deprecated for use on NUL-terminated destination strings
>> [1] and as such we should prefer more robust and less ambiguous string
>> interfaces.
>>
>> We expect netdev->name to be NUL-terminated based on its usage with
>> `strlen` and format strings:
>> |       if (strlen(netdev->name) < (IFNAMSIZ - 5)) {
>> |               sprintf(adapter->tx_ring->name, "%s-tx-0", netdev->name);
>>
>> Moreover, we do not need NUL-padding as netdev is already
>> zero-allocated:
>> |       netdev = alloc_etherdev(sizeof(struct igbvf_adapter));
>> ...
>> alloc_etherdev() -> alloc_etherdev_mq() -> alloc_etherdev_mqs() ->
>> alloc_netdev_mqs() ...
>> |       p = kvzalloc(alloc_size, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
>>
>> Considering the above, a suitable replacement is `strscpy` [2] due to
>> the fact that it guarantees NUL-termination on the destination buffer
>> without unnecessarily NUL-padding.
>>
>> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
>> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
>> Link: https://github.com/KSPP/linux/issues/90
>> Cc: linux-hardening@...r.kernel.org
>> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
>> ---
> 
> Thanks Justin for these patches, please make sure you mark the subject
> line as per the netdev rules:
> [PATCH net-next v1] etc etc
> 
> I'd also prefer they came in as part of one series with a good cover
> letter, at the very least for the Intel drivers, and you probably could
> combine any others (netdev) together up to the 15 patch limit.
> 
> Please mention how you found these issues, via automated tool or via
> coccinelle script, manual grepping, etc?
> 
> Thanks,
> Jesse

netdev rules: https://docs.kernel.org/process/maintainer-netdev.html

Also, please see my related series, that will probably conflict with
your changes but the two are making different changes.

https://lore.kernel.org/netdev/20231003183603.3887546-1-jesse.brandeburg@intel.com/