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

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Date:   Fri, 4 Mar 2022 23:55:35 +0800
From:   "Xiaoke Wang" <xkernel.wang@...mail.com>
To:     "Greg KH" <gregkh@...uxfoundation.org>
Cc:     "linux" <linux@...inikbrodowski.net>,
        "akpm" <akpm@...ux-foundation.org>,
        "pombredanne" <pombredanne@...b.com>,
        "arnd" <arnd@...db.de>,
        "luc.vanoostenryck" 
        <luc.vanoostenryck@...il.com>,
        "linux-kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] init/initramfs.c: check the return value of kstrdup()

On Fri, 04 Mar 2022 22:14:21 +0800, Greg KH <gregkh@...uxfoundation.org> wrote:
>> 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) {
>
> How can this fail?  Have you ever hit this in real life?
>
>> +kfree(de);
>> +panic_show_mem("can't duplicate dir name");
>
> Why are you freeing memory if you are panicing?
>
> How was this tested?

Thank you for taking the time.
I found this with a static tool, without dynamic testing.
kstrdup() allocates memory for copying the string and I noticed all the
other allocation functions in this file have the check for their return
value such as `de` on the above code. So I suppose this is also needed
to be checked and I intuitively add kfree() on the error path.
I'm sorry to bother you if this is actually unnecessary.

Regards,
Xiaoke Wang