linux-kernel - Re: [PATCH v2] ALSA: sound/isa/gus: check the return value of kstrdup()

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Date:   Mon, 13 Dec 2021 14:23:01 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Xiaoke Wang <xkernel.wang@...mail.com>
Cc:     perex@...ex.cz, tiwai@...e.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ALSA: sound/isa/gus: check the return value of kstrdup()

On Mon, 13 Dec 2021 11:52:32 +0100,
Xiaoke Wang wrote:
> 
> kstrdup() returns NULL when some internal memory errors happen, it is
> better to check the return value of it. Otherwise, we may not to be able
> to catch some memory errors in time.
> 
> Signed-off-by: Xiaoke Wang <xkernel.wang@...mail.com>
> ---
> Changes in v2:
>  - add the proper error handling.
> Thanks for the suggestions from Takashi Iwai. In the future, I'll pay 
> more attention to what he mentioned.

Thanks, now I applied as is.

BTW, when you look at the code carefully, you'll find that the memory
leaks may occur at the second and the third chunk in your patch. It's
not a fault of this change, but it's a bug in the original code.

Actually there are two issues -- one is about the incorrect return
value from snd_gf1_mem_xalloc() and another is the missing kfree of
block.name.  Will submit two fix patches as a follow up.


Takashi

> ---
> sound/isa/gus/gus_mem.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/isa/gus/gus_mem.c b/sound/isa/gus/gus_mem.c
> index ff9480f..4c691db 100644
> --- a/sound/isa/gus/gus_mem.c
> +++ b/sound/isa/gus/gus_mem.c
> @@ -199,6 +199,10 @@ struct snd_gf1_mem_block *snd_gf1_mem_alloc(struct snd_gf1_mem * alloc, int owne
>  		memcpy(&block.share_id, share_id, sizeof(block.share_id));
>  	block.owner = owner;
>  	block.name = kstrdup(name, GFP_KERNEL);
> +	if (block.name == NULL) {
> +		snd_gf1_mem_lock(alloc, 1);
> +		return NULL;
> +	}
>  	nblock = snd_gf1_mem_xalloc(alloc, &block);
>  	snd_gf1_mem_lock(alloc, 1);
>  	return nblock;
> @@ -237,13 +241,13 @@ int snd_gf1_mem_init(struct snd_gus_card * gus)
>  		block.ptr = 0;
>  		block.size = 1024;
>  		block.name = kstrdup("InterWave LFOs", GFP_KERNEL);
> -		if (snd_gf1_mem_xalloc(alloc, &block) == NULL)
> +		if (block.name == NULL || snd_gf1_mem_xalloc(alloc, &block) == NULL)
>  			return -ENOMEM;
>  	}
>  	block.ptr = gus->gf1.default_voice_address;
>  	block.size = 4;
>  	block.name = kstrdup("Voice default (NULL's)", GFP_KERNEL);
> -	if (snd_gf1_mem_xalloc(alloc, &block) == NULL)
> +	if (block.name == NULL || snd_gf1_mem_xalloc(alloc, &block) == NULL)
>  		return -ENOMEM;
>  #ifdef CONFIG_SND_DEBUG
>  	snd_card_ro_proc_new(gus->card, "gusmem", gus, snd_gf1_mem_info_read);
> -- 
>