linux-kernel - Re: [PATCH] s390/sclp: Add check for get_zeroed

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Message-ID: <20250217160117.21424B3d-hca@linux.ibm.com>
Date: Mon, 17 Feb 2025 17:01:17 +0100
From: Heiko Carstens <hca@...ux.ibm.com>
To: Haoxiang Li <haoxiang_li2024@....com>
Cc: gor@...ux.ibm.com, agordeev@...ux.ibm.com, borntraeger@...ux.ibm.com,
        svens@...ux.ibm.com, schwidefsky@...ibm.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] s390/sclp: Add check for get_zeroed_page()

On Mon, Feb 17, 2025 at 11:31:46PM +0800, Haoxiang Li wrote:
> Add check for the return value of get_zeroed_page() in
> sclp_console_init() to prevent null pointer dereference.
> 
> Fixes: 4c8f4794b61e ("[S390] sclp console: convert from bootmem to slab")
> Cc: stable@...r.kernel.org
> Signed-off-by: Haoxiang Li <haoxiang_li2024@....com>
> ---
>  drivers/s390/char/sclp_con.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/s390/char/sclp_con.c b/drivers/s390/char/sclp_con.c
> index e5d947c763ea..7447076b1ec1 100644
> --- a/drivers/s390/char/sclp_con.c
> +++ b/drivers/s390/char/sclp_con.c
> @@ -282,6 +282,8 @@ sclp_console_init(void)
>  	/* Allocate pages for output buffering */
>  	for (i = 0; i < sclp_console_pages; i++) {
>  		page = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
> +		if (!page)
> +			return -ENOMEM;
>  		list_add_tail(page, &sclp_con_pages);

We can add this check, however if this early allocation would fail a
null pointer dereference would be the last problem we would have to
think about.

Anyway:
Acked-by: Heiko Carstens <hca@...ux.ibm.com>