linux-kernel - Re: [PATCH] NFC: Fix error handling in nfc_genl_dump

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Message-ID: <3c0b6a08-cbaa-4e7e-8689-1fa716dd1525@kernel.org>
Date: Mon, 24 Nov 2025 09:24:02 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Ma Ke <make24@...as.ac.cn>, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
 linville@...driver.com, aloisio.almeida@...nbossa.org,
 johannes@...solutions.net, lauro.venancio@...nbossa.org,
 sameo@...ux.intel.com
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 akpm@...ux-foundation.org, stable@...r.kernel.org
Subject: Re: [PATCH] NFC: Fix error handling in nfc_genl_dump_targets

On 21/11/2025 03:27, Ma Ke wrote:
> nfc_genl_dump_targets() increments the device reference count via

Only in some cases, but you drop it unconditionally.

> nfc_get_device() but fails to decrement it properly. nfc_get_device()
> calls class_find_device() which internally calls get_device() to
> increment the reference count. No corresponding put_device() is made
> to decrement the reference count.
> 
> Add proper reference count decrementing using nfc_put_device() when
> the dump operation completes or encounters an error, ensuring balanced
> reference counting.
> 
> Found by code review.

Drop, there is no point nor need to say that humans did the work. This
actually rather suggests you used LLM and disguise your finding as "code
review".

No, LLM is not code review.

> 
> Cc: stable@...r.kernel.org
> Fixes: 4d12b8b129f1 ("NFC: add nfc generic netlink interface")
> Signed-off-by: Ma Ke <make24@...as.ac.cn>
> ---
>  net/nfc/netlink.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
> index a18e2c503da6..9ae138ee91dd 100644
> --- a/net/nfc/netlink.c
> +++ b/net/nfc/netlink.c
> @@ -159,6 +159,11 @@ static int nfc_genl_dump_targets(struct sk_buff *skb,
>  
>  	cb->args[0] = i;
>  
> +	if (rc < 0 || i >= dev->n_targets) {
> +		nfc_put_device(dev);
> +		cb->args[1] = 0;

Did you test it?


Best regards,
Krzysztof