linux-kernel - Re: [PATCH] init/initramfs.c: check the return value of kstrdup()

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Message-Id: <20220306172859.2a35d07284b6aee209b9dcfb@linux-foundation.org>
Date:   Sun, 6 Mar 2022 17:28:59 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     xkernel.wang@...mail.com
Cc:     linux@...inikbrodowski.net, pombredanne@...b.com,
        gregkh@...uxfoundation.org, arnd@...db.de,
        luc.vanoostenryck@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] init/initramfs.c: check the return value of kstrdup()

On Fri,  4 Mar 2022 17:27:34 +0800 xkernel.wang@...mail.com wrote:

> From: Xiaoke Wang <xkernel.wang@...mail.com>
> 
> kstrdup() is also a memory allocation function which is similar
> with kmalloc() in some way. Once some internal memory errors
> happen, it will return NULL. It is better to check the return
> value of it so to catch the memory error in time.
> 
> ...
>
> --- a/init/initramfs.c
> +++ b/init/initramfs.c
> @@ -139,8 +139,12 @@ static void __init dir_add(const char *name, time64_t mtime)
>  	struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL);
>  	if (!de)
>  		panic_show_mem("can't allocate dir_entry buffer");
> -	INIT_LIST_HEAD(&de->list);
>  	de->name = kstrdup(name, GFP_KERNEL);
> +	if (!de->name) {
> +		kfree(de);
> +		panic_show_mem("can't duplicate dir name");
> +	}
> +	INIT_LIST_HEAD(&de->list);
>  	de->mtime = mtime;
>  	list_add(&de->list, &dir_list);

We often assume that memory allocations cannot fail in __init code.  If
the kernel runs out of memory at this stage, we have very deep problems
and it's virtually impossible that execution would have got this far.