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From: Greg KH <>
To: KP Singh <>
	"José Oliveira" <>,
	"Rodrigo Branco" <>,
Subject: Re: [PATCH v3 1/2] x86/speculation: Allow enabling STIBP with legacy IBRS
Date: Mon, 27 Feb 2023 07:29:51 +0100	[thread overview]
Message-ID: <Y/> (raw)
In-Reply-To: <>

On Mon, Feb 27, 2023 at 07:05:40AM +0100, KP Singh wrote:
> When plain IBRS is enabled (not enhanced IBRS), the logic in
> spectre_v2_user_select_mitigation() determines that STIBP is not needed.
> The IBRS bit implicitly protects against cross-thread branch target
> injection. However, with legacy IBRS, the IBRS bit is cleared on
> returning to userspace for performance reasons which leaves userspace
> threads vulnerable to cross-thread branch target injection against which
> STIBP protects.
> Exclude IBRS from the spectre_v2_in_ibrs_mode() check to allow for
> enabling STIBP (through seccomp/prctl() by default or always-on, if
> selected by spectre_v2_user kernel cmdline parameter).
> Fixes: 7c693f54c873 ("x86/speculation: Add spectre_v2=ibrs option to support Kernel IBRS")
> Reported-by: José Oliveira <>
> Reported-by: Rodrigo Branco <>
> Cc:
> Signed-off-by: KP Singh <>
> ---
>  arch/x86/kernel/cpu/bugs.c | 26 +++++++++++++++++++-------
>  1 file changed, 19 insertions(+), 7 deletions(-)


This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- This looks like a new version of a previously submitted patch, but you
  did not list below the --- line any changes from the previous version.
  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/process/submitting-patches.rst for what
  needs to be done here to properly describe this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.


greg k-h's patch email bot

      parent reply	other threads:[~2023-02-27  6:30 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-27  6:05 [PATCH v3 1/2] x86/speculation: Allow enabling STIBP with legacy IBRS KP Singh
2023-02-27  6:05 ` [PATCH v3 2/2] Documentation/hw-vuln: Document the interaction between IBRS and STIBP KP Singh
2023-02-27  6:30   ` Greg KH
2023-02-27 19:58   ` [tip: x86/urgent] " tip-bot2 for KP Singh
2023-02-27  6:29 ` Greg KH [this message]

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