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Mon, 23 Mar 2026 11:48:17 -0700 (PDT) MIME-Version: 1.0 References: <20260322054309.898214-1-surenb@google.com> <20260322054309.898214-4-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Mon, 23 Mar 2026 11:48:05 -0700 X-Gm-Features: AQROBzAcISvCKuZDTq5gxGva_UwU6WnzRjvi5ru0PTUHh42qSaWhag7QAbSow20 Message-ID: Subject: Re: [PATCH v4 3/4] KVM: s390: avoid kvm_s390_handle_pv() error overwrite To: "Lorenzo Stoakes (Oracle)" Cc: akpm@linux-foundation.org, willy@infradead.org, david@kernel.org, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, lorenzo.stoakes@oracle.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, vbabka@suse.cz, jannh@google.com, rppt@kernel.org, mhocko@suse.com, pfalcato@suse.de, kees@kernel.org, maddy@linux.ibm.com, npiggin@gmail.com, mpe@ellerman.id.au, chleroy@kernel.org, borntraeger@linux.ibm.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com, gerald.schaefer@linux.ibm.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 4C6D940015 X-Stat-Signature: 3ikp9dunjhcdrtrgbg9y4dppwpt1r4rw X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1774291699-584924 X-HE-Meta: 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 FJcXEyFX jQT8ww5EU0cYSao1dd8wpGZEnRlg8WLjQOXbWyLRck3PCbiV9OlLayP/hxkGFRBcQYjTc6Lz8ztv8qx1Ay37NUlGTygWGmG+cthm0lhWow9Isg6P6FDfSozvLl7kWsEEtwzaajpi/iA2DUoudiCuhh+B9TEbKdCQDLjtvuXdsm3KICE67F/7eSHF/UyNHE9E84+9pyDkPVDQZO5nb4s1yfcp6nEXW+Xz2xp2/LQiriu6TsIDbVsDqPzRBNcjBXQnyLHxhnNDTmRzoGIdlsn+xDbrQPGZhq4bnu8RLzKL2boEK4XXUDpYsbSQTCQR4t/gDXOfdmZjEeO3F8BGHHqlFelvrEIKTfcFraC1AJbNWYT/4MsfYojyfy1iSyQqaTM/1ZTlIPxdxq3fXXhb7fS/ZnHnWsw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 23, 2026 at 10:53=E2=80=AFAM Lorenzo Stoakes (Oracle) wrote: > > On Sat, Mar 21, 2026 at 10:43:07PM -0700, Suren Baghdasaryan wrote: > > If kvm_s390_handle_pv() call fails its error code gets recorded but > > execution proceeds as if the call was successful. If the next call to > > copy_to_user() fails then the original error is overwritten. > > Is that really a big deal though, as you're returning an error in either = case? > > > The follow-up patch adds fatal signal checks during VMA walk, which > > makes it possible for kvm_s390_handle_pv() to return EINTR error. > > Without this fix any error including EINTR can be overwritten and > > original error will be lost. > > > > Change error handling for kvm_s390_handle_pv() to alter normal flow > > once failure happens. This is consistent with how kvm_arch_vm_ioctl > > handles errors for other ioctl commands. > > > > Signed-off-by: Suren Baghdasaryan > > --- > > arch/s390/kvm/kvm-s390.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > > index 3eb60aa932ec..ddad08c0926f 100644 > > --- a/arch/s390/kvm/kvm-s390.c > > +++ b/arch/s390/kvm/kvm-s390.c > > @@ -2947,6 +2947,8 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned= int ioctl, unsigned long arg) > > } > > /* must be called without kvm->lock */ > > r =3D kvm_s390_handle_pv(kvm, &args); > > + if (r) > > + break; > > if (copy_to_user(argp, &args, sizeof(args))) { > > Yeah as per Sashiko we probably need to copy_to_user() still. > > But in that case, do we even need a change at all? I'm not sure it really > matters which error code terminates things does it? I agree. I plan to drop this patch from the series (see my former reply) unless someone tells me otherwise. > > > r =3D -EFAULT; > > break; > > -- > > 2.53.0.1018.g2bb0e51243-goog > > > > Thanks, Lorenzo