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Mon, 12 Oct 2026 06:38:59 +0000 (GMT) Received: from tuxmaker.linux.ibm.com (unknown [9.87.85.9]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTPS; Mon, 12 Oct 2026 06:38:59 +0000 (GMT) From: Sven Schnelle To: Heiko Carstens Cc: Alexander Gordeev , Vasily Gorbik , Christian Borntraeger , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [PATCH] s390/extable: Fix mvcos instruction decoding In-Reply-To: <20261002102750.1994830-1-hca@linux.ibm.com> (Heiko Carstens's message of "Fri, 2 Oct 2026 12:27:50 +0200") References: <20261002102750.1994830-1-hca@linux.ibm.com> Date: Mon, 12 Oct 2026 08:38:59 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) 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-Proofpoint-Spam-Info: AW1haW4tMjYxMDEyMDAyNCBTYWx0ZWRfXwU8Gp3zqZ7qa zVHlsg+htH174M2RPGtPDV3TlsFAkVhK3KPKq1dJzSSKWLpHOygvogXnXnCeecM6QFH4T7r0JEL u5oF8hyZeyMM85K+ExjrWVY/VADJSF0= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDEyMDAyNCBTYWx0ZWRfX9gkFpmIeQbTb UoxTieT8BzZr8eC0gPiyWkA7YaCddWhQ50P6BtBcITESc9oP9MGokvgayCpsEny/eMERalfcyE1 c7V+GZTKyBdGl7dR7KqpSLOh7epSaJjltzDBIVkktsth+IHcnKuyh00gmJ/IXAzusH1aCcCTLqz UXZ54eITuvIr3MIW0CQg/DakN/cm3h2eUOUUqHqw3tou6LOP0FurLqS11Ny455LmPGJfOSDoQC4 ODMlCM3/g8KubXnecRTgm04gZZN6cRolLt9JBxS9ZUaqlmLrYT4QC6mGzQf30ThLdCJc3qtTsgq 644nBNr1YGyN2HG7dzumkeWCTkvcxCx2pilXPVeBWMqVLaUDYUFfDvcnHAKTeVGLTuqAsNv4NuU eoPVkH9ZRTvPxgxdg/7rDXj/bvPA+kASeD3LtMjAgBAO+JQLKdgjkkXAYGfCNfjItmkG0ZsaFCl jTO3WUKEAyUTfT9wGDQ== X-Authority-Analysis: v=2.4 cv=E6pYNqdl c=1 sm=1 tr=0 ts=6acc8088 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=4RnNsjVToRJwR0ODri8A:9 X-Proofpoint-ORIG-GUID: RSlqgEYwDxAwonlyXUnZeqBJUmPqe0wE X-Proofpoint-GUID: RSlqgEYwDxAwonlyXUnZeqBJUmPqe0wE X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-10-12_02,2026-10-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 phishscore=0 clxscore=1015 bulkscore=0 priorityscore=1501 spamscore=0 adultscore=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610120024 Heiko Carstens writes: > If either the b1 or b2 field of the mvcos instruction is zero, register > zero is not used for address computation; zero is used instead, according > to the architecture. ex_handler_ua_mvcos() incorrectly uses the real > contents of register zero. Fix this. > > This shouldn't be a problem for any generated code, since the compiler > would only generate such code if it is possible to prove at compile time > that either the source or destination address is within the first 4kb of > the designated address space. Such code should not exist (also confirmed > by an allyesconfig build and decoding all ~7000 mvcos instructions). > > Fixes: c488f5187a24 ("s390/uaccess: Shorten raw_copy_from_user() / raw_copy_to_user() inline assemblies") > Cc: stable@vger.kernel.org > Signed-off-by: Heiko Carstens > --- > arch/s390/mm/extable.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/s390/mm/extable.c b/arch/s390/mm/extable.c > index 7498e858c401..848855da9a70 100644 > --- a/arch/s390/mm/extable.c > +++ b/arch/s390/mm/extable.c > @@ -106,9 +106,9 @@ static bool ex_handler_ua_mvcos(const struct exception_table_entry *ex, > regs->psw.addr = extable_fixup(ex); > insn = (struct insn_ssf *)regs->psw.addr; > if (from) > - uaddr = regs->gprs[insn->b2] + insn->d2; > + uaddr = (insn->b2 ? regs->gprs[insn->b2] : 0) + insn->d2; > else > - uaddr = regs->gprs[insn->b1] + insn->d1; > + uaddr = (insn->b1 ? regs->gprs[insn->b1] : 0) + insn->d1; > remainder = PAGE_SIZE - (uaddr & (PAGE_SIZE - 1)); > if (regs->gprs[insn->r3] <= remainder) > remainder = 0; Reviewed-by: Sven Schnelle