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Mon, 10 Nov 2025 15:38:34 +0000 (GMT) From: "Marc Hartmayer" To: Claudio Imbrenda , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, nrb@linux.ibm.com, nsg@linux.ibm.com, seiden@linux.ibm.com, gra@linux.ibm.com, schlameuss@linux.ibm.com, hca@linux.ibm.com, svens@linux.ibm.com, agordeev@linux.ibm.com, gor@linux.ibm.com, ggala@linux.ibm.com, david@redhat.com Subject: Re: [PATCH v1 1/1] KVM: s390: Fix gmap_helper_zap_one_page() again In-Reply-To: <20251106152545.338188-1-imbrenda@linux.ibm.com> References: <20251106152545.338188-1-imbrenda@linux.ibm.com> Date: Mon, 10 Nov 2025 16:38:33 +0100 Message-ID: <87346l7v9i.fsf@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=Ss+dKfO0 c=1 sm=1 tr=0 ts=69120700 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=pknXBTohXVt6Cvpor-UA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTA4MDA5NSBTYWx0ZWRfX2zwed/t/ApLa f4rlvWj9QEs2BT/VketNC18m+DOIyUUG1zTiAJCTMgSCYAbhoyWLLSyaeYHg5ATQ2iI0hkzyAHa VulS+5gr3gw9ECbZhjxQKgSsWdgbxLyan2ILmqhj+FUKiWBDmOaC+KXTNx5hvg8ZlO6L+77S007 T/37mykupHkbSlny/9O0fUd4Rzuwfv0kgYwRYtl0tetMF99k456ZrusMsxRIDzV7sNt8EW5DC8R KQwEj4R9LIbZN14LvuHc1Cb9g1K/8NNnyFOWWCd8HnpWttWTq/8rY2NgH69dPQKC4zDN56FcK9R DAPTbkILI2B0+1elQPgPmM9hHk1Gm4gsyWtsMrW2SkLlPPdnAJM0UR8UjErZ70op3Pi9NZv1v1m UL2X8xn+mVn0nuW55b0FfyGCIoXFGQ== X-Proofpoint-GUID: LPxLY2YjJFAeJd2cnqic_Cz6afSrasmA X-Proofpoint-ORIG-GUID: LPxLY2YjJFAeJd2cnqic_Cz6afSrasmA X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-10_05,2025-11-10_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 suspectscore=0 impostorscore=0 bulkscore=0 phishscore=0 lowpriorityscore=0 adultscore=0 priorityscore=1501 spamscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511080095 On Thu, Nov 06, 2025 at 04:25 PM +0100, Claudio Imbrenda wrote: > A few checks were missing in gmap_helper_zap_one_page(), which can lead > to memory corruption in the guest under specific circumstances. > > Add the missing checks. > > Fixes: 5deafa27d9ae ("KVM: s390: Fix to clear PTE when discarding a swapped page") > Reported-by: Marc Hartmayer > Signed-off-by: Claudio Imbrenda > --- > arch/s390/mm/gmap_helpers.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/arch/s390/mm/gmap_helpers.c b/arch/s390/mm/gmap_helpers.c > index d4c3c36855e2..38a2d82cd88a 100644 > --- a/arch/s390/mm/gmap_helpers.c > +++ b/arch/s390/mm/gmap_helpers.c > @@ -47,6 +47,7 @@ static void ptep_zap_swap_entry(struct mm_struct *mm, swp_entry_t entry) > void gmap_helper_zap_one_page(struct mm_struct *mm, unsigned long vmaddr) > { > struct vm_area_struct *vma; > + unsigned long pgstev; > spinlock_t *ptl; > pgste_t pgste; > pte_t *ptep; > @@ -65,9 +66,13 @@ void gmap_helper_zap_one_page(struct mm_struct *mm, unsigned long vmaddr) > if (pte_swap(*ptep)) { > preempt_disable(); > pgste = pgste_get_lock(ptep); > + pgstev = pgste_val(pgste); > > - ptep_zap_swap_entry(mm, pte_to_swp_entry(*ptep)); > - pte_clear(mm, vmaddr, ptep); > + if ((pgstev & _PGSTE_GPS_USAGE_MASK) == _PGSTE_GPS_USAGE_UNUSED || > + (pgstev & _PGSTE_GPS_ZERO)) { > + ptep_zap_swap_entry(mm, pte_to_swp_entry(*ptep)); > + pte_clear(mm, vmaddr, ptep); > + } > > pgste_set_unlock(ptep, pgste); > preempt_enable(); > -- > 2.51.1 Thanks for the fix. Tested-by: Marc Hartmayer