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Wed, 9 Feb 2022 09:34:20 +0000 (GMT) Received: from [9.171.87.52] (unknown [9.171.87.52]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 9 Feb 2022 09:34:19 +0000 (GMT) Message-ID: <29ac0e5c-f77b-04b2-bbf5-cf5a5ca78921@linux.ibm.com> Date: Wed, 9 Feb 2022 10:34:19 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v2 05/11] KVM: s390: Add optional storage key checking to MEMOP IOCTL Content-Language: en-US From: Christian Borntraeger To: Janis Schoetterl-Glausch , Heiko Carstens , Janosch Frank , Konstantin Ryabitsev Cc: Alexander Gordeev , Claudio Imbrenda , David Hildenbrand , Jonathan Corbet , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Paolo Bonzini , Sven Schnelle , Vasily Gorbik References: <20220207165930.1608621-1-scgl@linux.ibm.com> <20220207165930.1608621-6-scgl@linux.ibm.com> <48d1678f-746c-dab6-5ec3-56397277f752@linux.ibm.com> <71f07914-d0b2-e98b-22b2-bc05f04df2da@linux.ibm.com> <6ea27647-fbbe-3962-03a0-8ca5340fc7fd@linux.ibm.com> In-Reply-To: <6ea27647-fbbe-3962-03a0-8ca5340fc7fd@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: JGM9Zf2mFAzgHbvz4-cjin-y2c5Ym3v7 X-Proofpoint-GUID: k8icOF-FvUBNOatk0Xme2-sWOtUNd3uB X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-02-09_05,2022-02-09_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 clxscore=1011 priorityscore=1501 phishscore=0 mlxlogscore=999 adultscore=0 bulkscore=0 malwarescore=0 lowpriorityscore=0 spamscore=0 mlxscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2202090062 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org CC Konstantin, I hope you can find the right people. Looks that my (and Janis) emaildid not make it to linux-s390 and kvm at vger lists. Message-ID: <6ea27647-fbbe-3962-03a0-8ca5340fc7fd@linux.ibm.com> Am 09.02.22 um 10:08 schrieb Christian Borntraeger: > > > Am 09.02.22 um 09:49 schrieb Janis Schoetterl-Glausch: >> On 2/9/22 08:34, Christian Borntraeger wrote: >>> Am 07.02.22 um 17:59 schrieb Janis Schoetterl-Glausch: >>>> User space needs a mechanism to perform key checked accesses when >>>> emulating instructions. >>>> >>>> The key can be passed as an additional argument. >>>> Having an additional argument is flexible, as user space can >>>> pass the guest PSW's key, in order to make an access the same way the >>>> CPU would, or pass another key if necessary. >>>> >>>> Signed-off-by: Janis Schoetterl-Glausch >>>> Acked-by: Janosch Frank >>>> Reviewed-by: Claudio Imbrenda >>>> --- >>>>    arch/s390/kvm/kvm-s390.c | 49 +++++++++++++++++++++++++++++++--------- >>>>    include/uapi/linux/kvm.h |  8 +++++-- >>>>    2 files changed, 44 insertions(+), 13 deletions(-) >>>> >>>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >>>> index cf347e1a4f17..71e61fb3f0d9 100644 >>>> --- a/arch/s390/kvm/kvm-s390.c >>>> +++ b/arch/s390/kvm/kvm-s390.c >>>> @@ -32,6 +32,7 @@ >>>>    #include >>>>    #include >>>>    #include >>>> +#include >>>>      #include >>>>    #include >>>> @@ -2359,6 +2360,11 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd) >>>>        return r; >>>>    } >>>>    +static bool access_key_invalid(u8 access_key) >>>> +{ >>>> +    return access_key > 0xf; >>>> +} >>>> + >>>>    long kvm_arch_vm_ioctl(struct file *filp, >>>>                   unsigned int ioctl, unsigned long arg) >>>>    { >>>> @@ -4687,34 +4693,54 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu, >>>>                      struct kvm_s390_mem_op *mop) >>>>    { >>>>        void __user *uaddr = (void __user *)mop->buf; >>>> +    u8 access_key = 0, ar = 0; >>>>        void *tmpbuf = NULL; >>>> +    bool check_reserved; >>>>        int r = 0; >>>>        const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION >>>> -                    | KVM_S390_MEMOP_F_CHECK_ONLY; >>>> +                    | KVM_S390_MEMOP_F_CHECK_ONLY >>>> +                    | KVM_S390_MEMOP_F_SKEY_PROTECTION; >>>>    -    if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size) >>>> +    if (mop->flags & ~supported_flags || !mop->size) >>>>            return -EINVAL; >>>> - >>>>        if (mop->size > MEM_OP_MAX_SIZE) >>>>            return -E2BIG; >>>> - >>>>        if (kvm_s390_pv_cpu_is_protected(vcpu)) >>>>            return -EINVAL; >>>> - >>>>        if (!(mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)) { >>>>            tmpbuf = vmalloc(mop->size); >>>>            if (!tmpbuf) >>>>                return -ENOMEM; >>>>        } >>>> +    ar = mop->ar; >>>> +    mop->ar = 0; >>> >>> Why this assignment to 0? >> >> It's so the check of reserved below works like that, they're all part of the anonymous union. > > Ah, I see. This is ugly :-) > >>> >>>> +    if (ar >= NUM_ACRS) >>>> +        return -EINVAL; >>>> +    if (mop->flags & KVM_S390_MEMOP_F_SKEY_PROTECTION) { >>>> +        access_key = mop->key; >>>> +        mop->key = 0; >>> >>> and this? I think we can leave mop unchanged. >>> >>> In fact, why do we add the ar and access_key variable? >>> This breaks the check from above (if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size))  into two checks >>> and it will create a memleak for tmpbuf. >> >> I can move the allocation down, goto out or get rid of the reserved check and keep everything as before. >> First is simpler, but second makes handling that case more explicit and might help in the future. > > Maybe add a reserved_02 field in the anon struct and check this for being zero and get rid of the local variables? > >> Patch 6 has the same issue in the vm ioctl handler. >>> >>> Simply use mop->key and mop->ar below and get rid of the local variables. >>> The structure has no concurrency and gcc will handle that just as the local variable. >>> >>> Other than that this looks good. >> >> [...] >>