linux-kernel - Re: [PATCH] s390/kvm: Replace sprintf with snprintf for buffer safety

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Message-ID: <3589d9b8-ccb4-4a55-8986-d14456218210@linux.ibm.com>
Date: Wed, 8 Oct 2025 14:47:49 +0200
From: Janosch Frank <frankja@...ux.ibm.com>
To: Josephine Pfeiffer <hi@...ie.lol>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev
 <agordeev@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] s390/kvm: Replace sprintf with snprintf for buffer safety

On 10/1/25 7:40 PM, Josephine Pfeiffer wrote:
> Replace sprintf() with snprintf() when formatting debug names to prevent
> potential buffer overflow. The debug_name buffer is 16 bytes, and while
> unlikely to overflow with current PIDs, using snprintf() provides proper
> bounds checking.
> 

Hey, we generally use "KVM: s390: Subject" so I'll fix this up.
Thanks, picked.

> Signed-off-by: Josephine Pfeiffer <hi@...ie.lol>
> ---
>   arch/s390/kvm/kvm-s390.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 6d51aa5f66be..005c117be086 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -3371,7 +3371,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>   			((char *) kvm->arch.sca + sca_offset);
>   	mutex_unlock(&kvm_lock);
>   
> -	sprintf(debug_name, "kvm-%u", current->pid);
> +	snprintf(debug_name, sizeof(debug_name), "kvm-%u", current->pid);
>   
>   	kvm->arch.dbf = debug_register(debug_name, 32, 1, 7 * sizeof(long));
>   	if (!kvm->arch.dbf)