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(1F2EF20A.nat.pool.telekom.hu. [31.46.242.10]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a6efe5262cdsm61350466b.117.2024.06.08.00.32.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 08 Jun 2024 00:32:21 -0700 (PDT) Sender: Ingo Molnar From: Ingo Molnar To: linux-kernel@vger.kernel.org Cc: Andy Lutomirski , Andrew Morton , Dave Hansen , Peter Zijlstra , Borislav Petkov , Brian Gerst , "H . Peter Anvin" , Linus Torvalds , Oleg Nesterov , Thomas Gleixner , Uros Bizjak Subject: [PATCH 6/9] x86/fpu: Make sure x86_task_fpu() doesn't get called for PF_KTHREAD tasks during exit Date: Sat, 8 Jun 2024 09:31:31 +0200 Message-ID: <20240608073134.264210-7-mingo@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240608073134.264210-1-mingo@kernel.org> References: <20240608073134.264210-1-mingo@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit fpu__drop() calls x86_task_fpu() unconditionally, while the FPU context area will not be present if it's the init task, and should not be in use when it's some other type of kthread. Return early for PF_KTHREAD tasks. The debug warning in x86_task_fpu() will catch any kthreads attempting to use the FPU save area. Signed-off-by: Ingo Molnar --- arch/x86/kernel/fpu/core.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index c85667c0695d..52d5843c886c 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -674,7 +674,13 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal, */ void fpu__drop(struct task_struct *tsk) { - struct fpu *fpu = x86_task_fpu(tsk); + struct fpu *fpu; + + /* PF_KTHREAD tasks do not use the FPU context area: */ + if (tsk->flags & PF_KTHREAD) + return; + + fpu = x86_task_fpu(tsk); preempt_disable(); -- 2.43.0