Messages in this thread | | | Subject | Re: arch/s390/kvm/gaccess.c:859 guest_range_to_gpas() error: uninitialized symbol 'prot'. | From | Janis Schoetterl-Glausch <> | Date | Thu, 18 Aug 2022 15:14:41 +0200 |
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On Thu, 2022-08-18 at 09:45 +0200, Janosch Frank wrote: > On 8/17/22 16:38, Claudio Imbrenda wrote: > > On Wed, 17 Aug 2022 12:30:11 +0200 > > Janis Schoetterl-Glausch <scgl@linux.ibm.com> wrote: > > > > > On 8/15/22 09:23, Dan Carpenter wrote: > > > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > > > > head: 69dac8e431af26173ca0a1ebc87054e01c585bcc > > > > commit: 7faa543df19bf62d4583a64d3902705747f2ad29 KVM: s390: gaccess: Refactor access address range check > > > > config: s390-randconfig-m031-20220812 (https://download.01.org/0day-ci/archive/20220814/202208140141.4uzWszG4-lkp@intel.com/config) > > > > compiler: s390-linux-gcc (GCC) 12.1.0 > > > > > > > > If you fix the issue, kindly add following tag where applicable > > > > Reported-by: kernel test robot <lkp@intel.com> > > > > Reported-by: Dan Carpenter <dan.carpenter@oracle.com> > > > > > > > > smatch warnings: > > > > arch/s390/kvm/gaccess.c:859 guest_range_to_gpas() error: uninitialized symbol 'prot'. > > > > > > > > vim +/prot +859 arch/s390/kvm/gaccess.c > > > > > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 831 static int guest_range_to_gpas(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 832 unsigned long *gpas, unsigned long len, > > > > 92c9632119b67f David Hildenbrand 2015-11-16 833 const union asce asce, enum gacc_mode mode) > > > > 2293897805c2fe Heiko Carstens 2014-01-01 834 { > > > > 2293897805c2fe Heiko Carstens 2014-01-01 835 psw_t *psw = &vcpu->arch.sie_block->gpsw; > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 836 unsigned int offset = offset_in_page(ga); > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 837 unsigned int fragment_len; > > > > cde0dcfb5df1db David Hildenbrand 2016-05-31 838 int lap_enabled, rc = 0; > > > > 6ae1574c2a24ee Christian Borntraeger 2017-06-07 839 enum prot_type prot; > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 840 unsigned long gpa; > > > > 2293897805c2fe Heiko Carstens 2014-01-01 841 > > > > 75a1812230ad7a Alexander Yarygin 2015-01-22 842 lap_enabled = low_address_protection_enabled(vcpu, asce); > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 843 while (min(PAGE_SIZE - offset, len) > 0) { > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 844 fragment_len = min(PAGE_SIZE - offset, len); > > > > 2293897805c2fe Heiko Carstens 2014-01-01 845 ga = kvm_s390_logical_to_effective(vcpu, ga); > > > > cde0dcfb5df1db David Hildenbrand 2016-05-31 846 if (mode == GACC_STORE && lap_enabled && is_low_address(ga)) > > > > cde0dcfb5df1db David Hildenbrand 2016-05-31 847 return trans_exc(vcpu, PGM_PROTECTION, ga, ar, mode, > > > > cde0dcfb5df1db David Hildenbrand 2016-05-31 848 PROT_TYPE_LA); > > > > a752598254016d Heiko Carstens 2017-06-03 849 if (psw_bits(*psw).dat) { > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 850 rc = guest_translate(vcpu, ga, &gpa, asce, mode, &prot); > > > > 2293897805c2fe Heiko Carstens 2014-01-01 851 if (rc < 0) > > > > 2293897805c2fe Heiko Carstens 2014-01-01 852 return rc; > > > > 2293897805c2fe Heiko Carstens 2014-01-01 853 } else { > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 854 gpa = kvm_s390_real_to_abs(vcpu, ga); > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 855 if (kvm_is_error_gpa(vcpu->kvm, gpa)) > > > > cde0dcfb5df1db David Hildenbrand 2016-05-31 856 rc = PGM_ADDRESSING; > > > > ^^^^^^^^^^^^^^^^^^^^ > > > > > > > > "rc" set but "prot" not initialized. > > > > > > prot is only used in case of PGM_PROTECTION. > > > Because of that, we could initialize prot to an arbitrary value, but that seems misleading and a bit ugly to me. > > > Alternatively, we could introduce a PROT_NONE. > > > Or we do nothing, since there is no actual problem. > > > @Janosch, @Claudio, what do you think? > > > > I agree that this is not a bug. > > > > It does look ugly, though, and all reasonable solutions are also ugly > > (each for a different reason). > > > > another solution is to set prot to an arbitrary value only in the if > > case marked above. that way prot is not arbitrarily initialized, and > > there is no need to add a new PROT_NONE (which then would need to be > > checked for in trans_exc) > > > > I do not have a strong opinion, though > > We either have a prot value or terminate is set, right?
It's independent of termination, we will have a valid value for prot if we terminate. And I guess it still would be undefined behavior even if the value were invalid and we terminate. > > So I'd opt to add a PROT_NONE (with a comment that it's only used for > init). If the statement above is true we can then also add a WARN if no > valid PROT_* is set in case if terminate isn't true and a PGM_PROTECTION > has been specified.
I think what I'll do is introduce PROT_NONE, but not initialize prot with it, but set prot to NONE whenever a code other than PGM_PROTECTION is set. > > > > > > > > > > > > > > > 2293897805c2fe Heiko Carstens 2014-01-01 857 } > > > > cde0dcfb5df1db David Hildenbrand 2016-05-31 858 if (rc) > > > > 6ae1574c2a24ee Christian Borntraeger 2017-06-07 @859 return trans_exc(vcpu, rc, ga, ar, mode, prot); > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 860 if (gpas) > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 861 *gpas++ = gpa; > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 862 offset = 0; > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 863 ga += fragment_len; > > > > 7faa543df19bf6 Janis Schoetterl-Glausch 2021-11-26 864 len -= fragment_len; > > > > 2293897805c2fe Heiko Carstens 2014-01-01 865 } > > > > 2293897805c2fe Heiko Carstens 2014-01-01 866 return 0; > > > > 2293897805c2fe Heiko Carstens 2014-01-01 867 } > > > > > > > > > >
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