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From: Borislav Petkov <bp@alien8.de>
To: Joerg Roedel <joro@8bytes.org>
Cc: x86@kernel.org, Hyunwook Baek <baekhw@google.com>,
	Joerg Roedel <jroedel@suse.de>,
	hpa@zytor.com, Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Jiri Slaby <jslaby@suse.cz>,
	Dan Williams <dan.j.williams@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Juergen Gross <jgross@suse.com>,
	Kees Cook <keescook@chromium.org>,
	David Rientjes <rientjes@google.com>,
	Cfir Cohen <cfir@google.com>, Erdem Aktas <erdemaktas@google.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mike Stunes <mstunes@vmware.com>,
	Sean Christopherson <seanjc@google.com>,
	Martin Radev <martin.b.radev@gmail.com>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v2 7/8] x86/insn: Extend error reporting from insn_fetch_from_user[_inatomic]()
Date: Fri, 21 May 2021 16:34:34 +0200	[thread overview]
Message-ID: <YKfE+gfK5AdE9ckm@zn.tnic> (raw)
In-Reply-To: <20210519135251.30093-8-joro@8bytes.org>

On Wed, May 19, 2021 at 03:52:50PM +0200, Joerg Roedel wrote:
> diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
> index 4eecb9c7c6a0..d8a057ba0895 100644
> --- a/arch/x86/lib/insn-eval.c
> +++ b/arch/x86/lib/insn-eval.c
> @@ -1442,27 +1442,36 @@ static int insn_get_effective_ip(struct pt_regs *regs, unsigned long *ip)
>   * insn_fetch_from_user() - Copy instruction bytes from user-space memory
>   * @regs:	Structure with register values as seen when entering kernel mode
>   * @buf:	Array to store the fetched instruction
> + * @copied:	Pointer to an int where the number of copied instruction bytes
> + *		is stored. Can be NULL.
>   *
>   * Gets the linear address of the instruction and copies the instruction bytes
>   * to the buf.
>   *
>   * Returns:
>   *
> - * Number of instruction bytes copied.
> + * -EINVAL if the linear address of the instruction could not be calculated
> + * -EFAULT if nothing was copied
> + *       0 on success
>   *
> - * 0 if nothing was copied.
>   */
> -int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE])
> +int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE],
> +			 int *copied)
>  {
>  	unsigned long ip;
>  	int not_copied;
> +	int bytes;
>  
>  	if (insn_get_effective_ip(regs, &ip))
> -		return 0;
> +		return -EINVAL;
>  
>  	not_copied = copy_from_user(buf, (void __user *)ip, MAX_INSN_SIZE);
>  
> -	return MAX_INSN_SIZE - not_copied;
> +	bytes = MAX_INSN_SIZE - not_copied;
> +	if (copied)
> +		*copied = bytes;
> +
> +	return bytes ? 0 : -EFAULT;

Why not simpler?

return value >= 0 says how many bytes were copied
return value < 0 means some kind of error

And then you don't need @copied...

Ditto for the other one.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

  reply	other threads:[~2021-05-21 14:34 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-19 13:52 [PATCH v2 0/8] x86/sev-es: Fixes for SEV-ES Guest Support Joerg Roedel
2021-05-19 13:52 ` [PATCH v2 1/8] x86/sev-es: Don't return NULL from sev_es_get_ghcb() Joerg Roedel
2021-05-19 13:52 ` [PATCH v2 2/8] x86/sev-es: Forward page-faults which happen during emulation Joerg Roedel
2021-05-19 13:52 ` [PATCH v2 3/8] x86/sev-es: Use __put_user()/__get_user() for data accesses Joerg Roedel
2021-05-19 13:52 ` [PATCH v2 4/8] x86/sev-es: Fix error message in runtime #VC handler Joerg Roedel
2021-05-19 13:52 ` [PATCH v2 5/8] x86/sev-es: Leave NMI-mode before sending signals Joerg Roedel
2021-05-19 17:54   ` Peter Zijlstra
2021-05-19 19:13     ` Joerg Roedel
2021-05-19 19:31       ` Peter Zijlstra
2021-05-19 13:52 ` [PATCH v2 6/8] x86/insn-eval: Make 0 a valid RIP for insn_get_effective_ip() Joerg Roedel
2021-05-19 13:52 ` [PATCH v2 7/8] x86/insn: Extend error reporting from insn_fetch_from_user[_inatomic]() Joerg Roedel
2021-05-21 14:34   ` Borislav Petkov [this message]
2021-05-19 13:52 ` [PATCH v2 8/8] x86/sev-es: Propagate #GP if getting linear instruction address failed Joerg Roedel

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