From: Borislav Petkov <bp@alien8.de>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Tony Luck <tony.luck@intel.com>,
Yu-cheng Yu <yu-cheng.yu@intel.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
syzbot+2067e764dbcd10721e2e@syzkaller.appspotmail.com,
stable@vger.kernel.org
Subject: Re: [patch V2 02/14] x86/fpu: Prevent state corruption in __fpu__restore_sig()
Date: Mon, 7 Jun 2021 10:49:02 +0200 [thread overview]
Message-ID: <YL3dfjIM9YHTW5S2@zn.tnic> (raw)
In-Reply-To: <20210606001323.067157324@linutronix.de>
On Sun, Jun 06, 2021 at 01:47:44AM +0200, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
>
> The non-compacted slowpath uses __copy_from_user() and copies the entire
> user buffer into the kernel buffer, verbatim. This means that the kernel
> buffer may now contain entirely invalid state on which XRSTOR will #GP.
> validate_user_xstate_header() can detect some of that corruption, but that
> leaves the onus on callers to clear the buffer.
>
> Prior to XSAVES support it was possible just to reinitialize the buffer,
> completely, but with supervisor states that is not longer possible as the
> buffer clearing code split got it backwards. Fixing that is possible, but
> not corrupting the state in the first place is more robust.
>
> Avoid corruption of the kernel XSAVE buffer by using copy_user_to_xstate()
> which validates the XSAVE header contents before copying the actual states
> to the kernel. copy_user_to_xstate() was previously only called for
> compacted-format kernel buffers, but it works for both compacted and
> non-compacted forms.
>
> Using it for the non-compacted form is slower because of multiple
> __copy_from_user() operations, but that cost is less important than robust
> code in an already slow path.
>
> [ Changelog polished by Dave Hansen ]
>
> Fixes: b860eb8dce59 ("x86/fpu/xstate: Define new functions for clearing fpregs and xstates")
> Reported-by: syzbot+2067e764dbcd10721e2e@syzkaller.appspotmail.com
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: stable@vger.kernel.org
> ---
> V2: Removed the make validate_user_xstate_header() static hunks (Borislav)
> ---
> arch/x86/kernel/fpu/signal.c | 9 +--------
> 1 file changed, 1 insertion(+), 8 deletions(-)
Very nice.
Reviewed-by: Borislav Petkov <bp@suse.de>
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2021-06-07 8:49 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-05 23:47 [patch V2 00/14] x86/fpu: Mop up XSAVES and related damage Thomas Gleixner
2021-06-05 23:47 ` [patch V2 01/14] selftests/x86: Test signal frame XSTATE header corruption handling Thomas Gleixner
2021-06-05 23:47 ` [patch V2 02/14] x86/fpu: Prevent state corruption in __fpu__restore_sig() Thomas Gleixner
2021-06-07 8:49 ` Borislav Petkov [this message]
2021-06-05 23:47 ` [patch V2 03/14] x86/fpu: Invalidate FPU state after a failed XRSTOR from a user buffer Thomas Gleixner
2021-06-05 23:47 ` [patch V2 04/14] x86/pkru: Make the fpinit state update work Thomas Gleixner
2021-06-07 15:18 ` Borislav Petkov
2021-06-05 23:47 ` [patch V2 05/14] x86/fpu: Limit xstate copy size in xstateregs_set() Thomas Gleixner
2021-06-05 23:47 ` [patch V2 06/14] x86/fpu: Sanitize xstateregs_set() Thomas Gleixner
2021-06-07 19:39 ` Borislav Petkov
2021-06-05 23:47 ` [patch V2 07/14] x86/fpu: Add address range checks to copy_user_to_xstate() Thomas Gleixner
2021-06-05 23:47 ` [patch V2 08/14] x86/fpu: Move inlines where they belong Thomas Gleixner
2021-06-05 23:47 ` [patch V2 09/14] x86/cpu: Sanitize X86_FEATURE_OSPKE Thomas Gleixner
2021-06-05 23:47 ` [patch V2 10/14] x86/fpu: Rename fpu__clear_all() to fpu_flush_thread() Thomas Gleixner
2021-06-05 23:47 ` [patch V2 11/14] x86/pkru: Provide pkru_get_init_value() Thomas Gleixner
2021-06-05 23:47 ` [patch V2 12/14] x86/fpu: Clean up the fpu__clear() variants Thomas Gleixner
2021-06-05 23:47 ` [patch V2 13/14] x86/fpu: Rename xstate copy functions which are related to UABI Thomas Gleixner
2021-06-05 23:47 ` [patch V2 14/14] x86/fpu: Deduplicate copy_uabi_from_user/kernel_to_xstate() Thomas Gleixner
2021-06-07 13:02 ` [patch V2 00/14] x86/fpu: Mop up XSAVES and related damage Thomas Gleixner
2021-06-07 13:36 ` Dave Hansen
2021-06-07 14:08 ` Thomas Gleixner
2021-06-07 16:38 ` Dave Hansen
2021-06-07 22:51 ` Thomas Gleixner
2021-06-08 14:47 ` Dave Hansen
2021-06-08 11:17 ` Thomas Gleixner
2021-06-08 12:27 ` Thomas Gleixner
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YL3dfjIM9YHTW5S2@zn.tnic \
--to=bp@alien8.de \
--cc=bigeasy@linutronix.de \
--cc=dave.hansen@linux.intel.com \
--cc=fenghua.yu@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=stable@vger.kernel.org \
--cc=syzbot+2067e764dbcd10721e2e@syzkaller.appspotmail.com \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.com \
--cc=x86@kernel.org \
--cc=yu-cheng.yu@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).