linux-kernel - [patch 12/21] x86/fpu: Do not leak fpstate pointer on fork

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Date:   Wed, 13 Oct 2021 16:55:43 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Chang S. Bae" <chang.seok.bae@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Subject: [patch 12/21] x86/fpu: Do not leak fpstate pointer on fork

If fork fails early then the copied task struct would carry the fpstate
pointer of the parent task.

Not a problem right now, but later when dynamically allocated buffers are
available, keeping the pointer might result in freeing the parents
buffer. Set it to NULL which prevents that. If fork reaches clone_thread,
the pointer will be correctly set to the new task context.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/process.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -87,6 +87,8 @@ int arch_dup_task_struct(struct task_str
 #ifdef CONFIG_VM86
 	dst->thread.vm86 = NULL;
 #endif
+	/* Drop the copied pointer to current's fpstate */
+	dst->thread.fpu.fpstate = NULL;
 	return 0;
 }