linux-hardening - Re: [PATCH] pstore/ram_core: Improve exception handling in persistent_ram

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Message-ID: <202402011013.025B9EDDC@keescook>
Date: Thu, 1 Feb 2024 10:13:50 -0800
From: Kees Cook <keescook@...omium.org>
To: Markus Elfring <Markus.Elfring@....de>
Cc: linux-hardening@...r.kernel.org, kernel-janitors@...r.kernel.org,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	Tony Luck <tony.luck@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Kunwu Chan <chentao@...inos.cn>
Subject: Re: [PATCH] pstore/ram_core: Improve exception handling in
 persistent_ram_new()

On Thu, Jan 18, 2024 at 03:06:53PM +0100, Markus Elfring wrote:
> From: Markus Elfring <elfring@...rs.sourceforge.net>
> Date: Thu, 18 Jan 2024 14:57:21 +0100
> 
> * Omit an initialisation (for the variable “ret”)
>   which became unnecessary with this refactoring
>   because a memory allocation failure will be directly indicated
>   by a corresponding return statement in an if branch.
> 
> * Move a call of the function “kstrdup” before two other statements.
> 
> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>

Thanks for you patch!

I've decided not to apply it because I prefer having a single exit path
for error handling, and it works as-is already.

-Kees

> ---
>  fs/pstore/ram_core.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
> index f1848cdd6d34..5047a8502e17 100644
> --- a/fs/pstore/ram_core.c
> +++ b/fs/pstore/ram_core.c
> @@ -586,21 +586,23 @@ struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
>  			unsigned int memtype, u32 flags, char *label)
>  {
>  	struct persistent_ram_zone *prz;
> -	int ret = -ENOMEM;
> +	int ret;
> 
>  	prz = kzalloc(sizeof(struct persistent_ram_zone), GFP_KERNEL);
>  	if (!prz) {
>  		pr_err("failed to allocate persistent ram zone\n");
> -		goto err;
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	prz->label = kstrdup(label, GFP_KERNEL);
> +	if (!prz->label) {
> +		kfree(prz);
> +		return ERR_PTR(-ENOMEM);
>  	}
> 
>  	/* Initialize general buffer state. */
>  	raw_spin_lock_init(&prz->buffer_lock);
>  	prz->flags = flags;
> -	prz->label = kstrdup(label, GFP_KERNEL);
> -	if (!prz->label)
> -		goto err;
> -
>  	ret = persistent_ram_buffer_map(start, size, prz, memtype);
>  	if (ret)
>  		goto err;
> --
> 2.43.0
> 

-- 
Kees Cook