linux-kernel - [PATCH] KVM: x86: hyper-v: fix type of valid_bank

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Message-Id: <20220519171504.1238724-1-yury.norov@gmail.com>
Date:   Thu, 19 May 2022 10:15:04 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Yury Norov <yury.norov@...il.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        kernel test robot <lkp@...el.com>
Subject: [PATCH] KVM: x86: hyper-v: fix type of valid_bank_mask

In kvm_hv_flush_tlb(), valid_bank_mask is declared as unsigned long,
but is used as u64, which is wrong for i386, and has been spotted by
LKP after applying "KVM: x86: hyper-v: replace bitmap_weight() with
hweight64()"

https://lore.kernel.org/lkml/20220510154750.212913-12-yury.norov@gmail.com/

But it's wrong even without that patch because now bitmap_weight()
dereferences a word after valid_bank_mask on i386.

>> include/asm-generic/bitops/const_hweight.h:21:76: warning: right shift count >= width of type
+[-Wshift-count-overflow]
      21 | #define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32))
         |                                                                            ^~
   include/asm-generic/bitops/const_hweight.h:10:16: note: in definition of macro '__const_hweight8'
      10 |          ((!!((w) & (1ULL << 0))) +     \
         |                ^
   include/asm-generic/bitops/const_hweight.h:20:31: note: in expansion of macro '__const_hweight16'
      20 | #define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >> 16))
         |                               ^~~~~~~~~~~~~~~~~
   include/asm-generic/bitops/const_hweight.h:21:54: note: in expansion of macro '__const_hweight32'
      21 | #define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32))
         |                                                      ^~~~~~~~~~~~~~~~~
   include/asm-generic/bitops/const_hweight.h:29:49: note: in expansion of macro '__const_hweight64'
      29 | #define hweight64(w) (__builtin_constant_p(w) ? __const_hweight64(w) : __arch_hweight64(w))
         |                                                 ^~~~~~~~~~~~~~~~~
   arch/x86/kvm/hyperv.c:1983:36: note: in expansion of macro 'hweight64'
    1983 |                 if (hc->var_cnt != hweight64(valid_bank_mask))
         |                                    ^~~~~~~~~

CC: Borislav Petkov <bp@...en8.de>
CC: Dave Hansen <dave.hansen@...ux.intel.com>
CC: H. Peter Anvin <hpa@...or.com>
CC: Ingo Molnar <mingo@...hat.com>
CC: Jim Mattson <jmattson@...gle.com>
CC: Joerg Roedel <joro@...tes.org>
CC: Paolo Bonzini <pbonzini@...hat.com>
CC: Sean Christopherson <seanjc@...gle.com>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Vitaly Kuznetsov <vkuznets@...hat.com>
CC: Wanpeng Li <wanpengli@...cent.com>
CC: kvm@...r.kernel.org
CC: linux-kernel@...r.kernel.org
CC: x86@...nel.org
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 arch/x86/kvm/hyperv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 58baf7f9acce..c8ca95d4e4e9 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1938,7 +1938,7 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
 	struct hv_send_ipi_ex send_ipi_ex;
 	struct hv_send_ipi send_ipi;
 	DECLARE_BITMAP(vcpu_mask, KVM_MAX_VCPUS);
-	unsigned long valid_bank_mask;
+	u64 valid_bank_mask;
 	u64 sparse_banks[KVM_HV_MAX_SPARSE_VCPU_SET_BITS];
 	u32 vector;
 	bool all_cpus;
-- 
2.32.0