linux-kernel - Re: [PATCH] arch: x86: kvm: x86.c: Cleaning up uninitialized variables

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:	Tue, 03 Jun 2014 17:06:12 +0400
From:	Michael Tokarev <mjt@....msk.ru>
To:	Paolo Bonzini <pbonzini@...hat.com>,
	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>,
	Gleb Natapov <gleb@...nel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arch: x86: kvm: x86.c:  Cleaning up uninitialized variables

03.06.2014 16:04, Paolo Bonzini wrote:
> Il 01/06/2014 01:05, Rickard Strandqvist ha scritto:
>> There is a risk that the variable will be used without being initialized.
>>
>> This was largely found by using a static code analysis program called cppcheck.
>>
>> Signed-off-by: Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
> 
> No, there isn't.  The full context looks like this:
> 
>         longmode = is_long_mode(vcpu) && cs_l == 1;
>         if (!longmode) {
>                 param = ((u64)kvm_register_read(vcpu, VCPU_REGS_RDX) << 32) |
>                         (kvm_register_read(vcpu, VCPU_REGS_RAX) & 0xffffffff);
>                 ingpa = ((u64)kvm_register_read(vcpu, VCPU_REGS_RBX) << 32) |
>                         (kvm_register_read(vcpu, VCPU_REGS_RCX) & 0xffffffff);
>                 outgpa = ((u64)kvm_register_read(vcpu, VCPU_REGS_RDI) << 32) |
>                         (kvm_register_read(vcpu, VCPU_REGS_RSI) & 0xffffffff);
>         }
> #ifdef CONFIG_X86_64
>         else {
>                 param = kvm_register_read(vcpu, VCPU_REGS_RCX);
>                 ingpa = kvm_register_read(vcpu, VCPU_REGS_RDX);
>                 outgpa = kvm_register_read(vcpu, VCPU_REGS_R8);
>         }
> #endif
> 
> and longmode must be zero if !CONFIG_X86_64:

This is not the first time this code is attempted to be changed.

Maybe adding an additional #ifdef..endif around the longmode
assignment and the "if" above will solve this for good?

Or maybe something like this:

 #ifdef CONFIG_X86_64
         if (!(is_long_mode(vcpu) && cs_l == 1)) {
 #else
         if (1) {
 #endif
                 param = ((u64)kvm_register_read(vcpu, VCPU_REGS_RDX) << 32) |
                         (kvm_register_read(vcpu, VCPU_REGS_RAX) & 0xffffffff);
                 ingpa = ((u64)kvm_register_read(vcpu, VCPU_REGS_RBX) << 32) |
                         (kvm_register_read(vcpu, VCPU_REGS_RCX) & 0xffffffff);
                 outgpa = ((u64)kvm_register_read(vcpu, VCPU_REGS_RDI) << 32) |
                         (kvm_register_read(vcpu, VCPU_REGS_RSI) & 0xffffffff);
         }
         else {
                 param = kvm_register_read(vcpu, VCPU_REGS_RCX);
                 ingpa = kvm_register_read(vcpu, VCPU_REGS_RDX);
                 outgpa = kvm_register_read(vcpu, VCPU_REGS_R8);
         }

, to make it all explicit and obvious?

Thanks,

/mjt

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/