Messages in this thread | | | Date | Thu, 18 Aug 2022 09:45:44 +0200 | From | Janosch Frank <> | Subject | Re: arch/s390/kvm/gaccess.c:859 guest_range_to_gpas() error: uninitialized symbol 'prot'. |
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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?
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.
> >> >>> >>> 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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