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

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Message-ID: <s5hilvsesp3.wl-tiwai@suse.de>
Date:   Mon, 13 Dec 2021 10:54:00 +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] ALSA: sound/isa/gus: check the return value of kstrdup()

On Mon, 13 Dec 2021 09:06:47 +0100,
Xiaoke Wang wrote:
> 
> Note: Compare with the last email, this one is using my full name.
> 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>

The patch again forgot about the proper error handling...
This will leave the mutex unbalanced.

Please be careful when writing this kind of fix at the next time.
Many code paths require the proper error handling, e.g. freeing the
rest memory or unlock/lock something.

In this particular case, snd_gf1_mem_lock(alloc, 1) is needed at the
first chunk.

And, the easiest way to fix would be to have a NULL check in
snd_gf1_mem_xalloc().  Then that will cover all callers by once.


thanks,

Takashi

> ---
>  sound/isa/gus/gus_mem.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/isa/gus/gus_mem.c b/sound/isa/gus/gus_mem.c
> index ff9480f..f8d915f 100644
> --- a/sound/isa/gus/gus_mem.c
> +++ b/sound/isa/gus/gus_mem.c
> @@ -199,6 +199,8 @@ 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)
> +		return NULL;
>  	nblock = snd_gf1_mem_xalloc(alloc, &block);
>  	snd_gf1_mem_lock(alloc, 1);
>  	return nblock;
> @@ -237,13 +239,13 @@ 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);
> -- 
>