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From: "tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@suse.de>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: x86/fpu] x86/fpu: Remove pointless memset in fpu_clone()
Date: Wed, 20 Oct 2021 13:44:42 -0000	[thread overview]
Message-ID: <163473748299.25758.1764135013570035920.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20211015011538.722854569@linutronix.de>

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     01f9f62d3ae75077a54a11d2777082f1e58e2d9f
Gitweb:        https://git.kernel.org/tip/01f9f62d3ae75077a54a11d2777082f1e58e2d9f
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Fri, 15 Oct 2021 03:16:02 +02:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Wed, 20 Oct 2021 15:27:26 +02:00

x86/fpu: Remove pointless memset in fpu_clone()

Zeroing the forked task's FPU registers buffer to avoid leaking init
optimized stale data into the clone is a pointless exercise for the case
where the current task has TIF_NEED_FPU_LOAD set. In that case, the FPU
registers state is copied from current's FPU register buffer which can
contain stale init optimized data as well.

The alledged information leak is non-existant because this stale init
optimized data is used nowhere and cannot leak anywhere.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211015011538.722854569@linutronix.de
---
 arch/x86/kernel/fpu/core.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 7ada7bd..191269e 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -260,12 +260,6 @@ int fpu_clone(struct task_struct *dst)
 		return 0;
 
 	/*
-	 * Don't let 'init optimized' areas of the XSAVE area
-	 * leak into the child task:
-	 */
-	memset(&dst_fpu->state.xsave, 0, fpu_kernel_xstate_size);
-
-	/*
 	 * If the FPU registers are not owned by current just memcpy() the
 	 * state.  Otherwise save the FPU registers directly into the
 	 * child's FPU context, without any memory-to-memory copying.

  reply	other threads:[~2021-10-20 13:46 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-15  1:15 [patch V2 00/30] x86/fpu: Preparatory cleanups for AMX support (part 1) Thomas Gleixner
2021-10-15  1:15 ` [patch V2 01/30] x86/fpu: Remove pointless argument from switch_fpu_finish() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:15 ` [patch V2 02/30] x86/fpu: Update stale comments Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:15 ` [patch V2 03/30] x86/pkru: Remove useless include Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:15 ` [patch V2 04/30] x86/fpu: Restrict xsaves()/xrstors() to independent states Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 05/30] x86/fpu: Cleanup the on_boot_cpu clutter Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 06/30] x86/fpu: Remove pointless memset in fpu_clone() Thomas Gleixner
2021-10-20 13:44   ` tip-bot2 for Thomas Gleixner [this message]
2021-10-15  1:16 ` [patch V2 07/30] x86/process: Clone FPU in copy_thread() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 08/30] x86/fpu: Do not inherit FPU context for kernel and IO worker threads Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 09/30] x86/fpu: Cleanup xstate xcomp_bv initialization Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 10/30] x86/fpu/xstate: Provide and use for_each_xfeature() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 11/30] x86/fpu/xstate: Mark all init only functions __init Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 12/30] x86/fpu: Move KVMs FPU swapping to FPU core Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 13/30] x86/fpu: Replace KVMs home brewed FPU copy from user Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 14/30] x86/fpu: Rework copy_xstate_to_uabi_buf() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 15/30] x86/fpu: Replace KVMs home brewed FPU copy to user Thomas Gleixner
2021-10-21 15:12   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 16/30] x86/fpu: Mark fpu__init_prepare_fx_sw_frame() as __init Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 17/30] x86/fpu: Move context switch and exit to user inlines into sched.h Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 18/30] x86/fpu: Clean up cpu feature tests Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] x86/fpu: Clean up CPU " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 19/30] x86/fpu: Make os_xrstor_booting() private Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 20/30] x86/fpu: Move os_xsave() and os_xrstor() to core Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 21/30] x86/fpu: Move legacy ASM wrappers " Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 22/30] x86/fpu: Make WARN_ON_FPU() private Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 23/30] x86/fpu: Move fpregs_restore_userregs() to core Thomas Gleixner
2021-10-19 18:11   ` Borislav Petkov
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 24/30] x86/fpu: Move mxcsr related code " Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 25/30] x86/fpu: Move fpstate functions to api.h Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 26/30] x86/fpu: Remove internal.h dependency from fpu/signal.h Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 27/30] x86/sev: Include fpu/xcr.h Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 28/30] x86/fpu: Mop up the internal.h leftovers Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 29/30] x86/fpu: Replace the includes of fpu/internal.h Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-15  1:16 ` [patch V2 30/30] x86/fpu: Provide a proper function for ex_handler_fprestore() Thomas Gleixner
2021-10-20 13:44   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner

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