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Fri, 4 Sep 2020 10:35:45 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AF538AE04D; Fri, 4 Sep 2020 10:35:44 +0000 (GMT) Received: from osiris (unknown [9.171.25.186]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Fri, 4 Sep 2020 10:35:44 +0000 (GMT) Date: Fri, 4 Sep 2020 12:35:43 +0200 From: Heiko Carstens To: Janosch Frank Cc: linux-s390@vger.kernel.org, borntraeger@de.ibm.com, gor@linux.ibm.com, imbrenda@linux.ibm.com, kvm@vger.kernel.org, david@redhat.com Subject: Re: [PATCH 2/2] s390x: Add 3f program exception handler Message-ID: <20200904103543.GD6075@osiris> References: <20200903131435.2535-1-frankja@linux.ibm.com> <20200903131435.2535-3-frankja@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200903131435.2535-3-frankja@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-09-04_05:2020-09-04,2020-09-04 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 phishscore=0 mlxlogscore=999 lowpriorityscore=0 bulkscore=0 adultscore=0 priorityscore=1501 impostorscore=0 suspectscore=1 spamscore=0 mlxscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009040093 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Sep 03, 2020 at 09:14:35AM -0400, Janosch Frank wrote: > Program exception 3f (secure storage violation) can only be detected > when the CPU is running in SIE with a format 4 state description, > e.g. running a protected guest. Because of this and because user > space partly controls the guest memory mapping and can trigger this > exception, we want to send a SIGSEGV to the process running the guest > and not panic the kernel. > > Signed-off-by: Janosch Frank > CC: # 5.7+ > Fixes: 084ea4d611a3 ("s390/mm: add (non)secure page access exceptions handlers") > Reviewed-by: Claudio Imbrenda > --- > arch/s390/kernel/pgm_check.S | 2 +- > arch/s390/mm/fault.c | 23 +++++++++++++++++++++++ > 2 files changed, 24 insertions(+), 1 deletion(-) > > diff --git a/arch/s390/kernel/pgm_check.S b/arch/s390/kernel/pgm_check.S > index 2c27907a5ffc..9a92638360ee 100644 > --- a/arch/s390/kernel/pgm_check.S > +++ b/arch/s390/kernel/pgm_check.S > @@ -80,7 +80,7 @@ PGM_CHECK(do_dat_exception) /* 3b */ > PGM_CHECK_DEFAULT /* 3c */ > PGM_CHECK(do_secure_storage_access) /* 3d */ > PGM_CHECK(do_non_secure_storage_access) /* 3e */ > -PGM_CHECK_DEFAULT /* 3f */ > +PGM_CHECK(do_secure_storage_violation) /* 3f */ > PGM_CHECK(monitor_event_exception) /* 40 */ > PGM_CHECK_DEFAULT /* 41 */ > PGM_CHECK_DEFAULT /* 42 */ > diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c > index 4c8c063bce5b..20abb7c5c540 100644 > --- a/arch/s390/mm/fault.c > +++ b/arch/s390/mm/fault.c > @@ -859,6 +859,24 @@ void do_non_secure_storage_access(struct pt_regs *regs) > } > NOKPROBE_SYMBOL(do_non_secure_storage_access); > > +void do_secure_storage_violation(struct pt_regs *regs) > +{ > + char buf[TASK_COMM_LEN]; > + > + /* > + * Either KVM messed up the secure guest mapping or the same > + * page is mapped into multiple secure guests. > + * > + * This exception is only triggered when a guest 2 is running > + * and can therefore never occur in kernel context. > + */ > + printk_ratelimited(KERN_WARNING > + "Secure storage violation in task: %s, pid %d\n", > + get_task_comm(buf, current), task_pid_nr(current)); Why get_task_comm() and task_pid_nr() instead of simply current->comm and current->pid? Also: is the dmesg message of any value? > + send_sig(SIGSEGV, current, 0); > +} > +NOKPROBE_SYMBOL(do_secure_storage_violation); Why is this NOKPROBE? Can this deadlock?