linux-kernel - Re: mainline build failure due to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 13 Jul 2022 13:35:22 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Sudip Mukherjee (Codethink)" <sudipm.mukherjee@...il.com>
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>, Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: mainline build failure due to fc02735b14ff ("KVM: VMX: Prevent
 guest RSB poisoning attacks with eIBRS")

On Wed, Jul 13, 2022 at 12:28:38PM +0100, Sudip Mukherjee (Codethink) wrote:
> Hi All,
> 
> The latest mainline kernel branch fails to build for x86_64 allmodconfig
> with clang and the error is:
> 
> arch/x86/kernel/cpu/bugs.c:58:21: error: section attribute is specified on redeclared variable [-Werror,-Wsection]
> DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
>                     ^
> ./arch/x86/include/asm/nospec-branch.h:283:12: note: previous declaration is here
> extern u64 x86_spec_ctrl_current;
> 
> 
> git bisect pointed to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
> 
> I will be happy to test any patch or provide any extra log if needed.

I suspect something like this will do.

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index bb05ed4f46bd..6398d39e66b0 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -280,7 +280,7 @@ static inline void indirect_branch_prediction_barrier(void)
 
 /* The Intel SPEC CTRL MSR base value cache */
 extern u64 x86_spec_ctrl_base;
-extern u64 x86_spec_ctrl_current;
+DECLARE_PER_CPU(u64, x86_spec_ctrl_current);
 extern void write_spec_ctrl_current(u64 val, bool force);
 extern u64 spec_ctrl_current(void);