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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id f144sm40062qke.132.2019.09.26.12.09.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Sep 2019 12:09:27 -0700 (PDT) From: Masayoshi Mizuma To: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org Cc: Masayoshi Mizuma , Masayoshi Mizuma , linux-kernel@vger.kernel.org Subject: [PATCH 1/1] arm64/sve: Fix wrong free for task->thread.sve_state Date: Thu, 26 Sep 2019 15:08:46 -0400 Message-Id: <20190926190846.3072-2-msys.mizuma@gmail.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190926190846.3072-1-msys.mizuma@gmail.com> References: <20190926190846.3072-1-msys.mizuma@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Masayoshi Mizuma The system which has SVE feature crashed because of the memory pointed by task->thread.sve_state was destroyed by someone. That is because sve_state is freed while the forking the child process. The child process has the pointer of sve_state which is same as the parent's because the child's task_struct is copied from the parent's one. If the copy_process() fails as an error on somewhere, for example, copy_creds(), then the sve_state is freed even if the parent is alive. The flow is as follows. copy_process p = dup_task_struct => arch_dup_task_struct *dst = *src; // copy the entire region. : retval = copy_creds if (retval < 0) goto bad_fork_free; : bad_fork_free: ... delayed_free_task(p); => free_task => arch_release_task_struct => fpsimd_release_task => __sve_free => kfree(task->thread.sve_state); // free the parent's sve_state Add a flag in task->thread which shows the fork is in progress. If the fork is in progress, that means the child has the pointer to the parent's sve_state, doesn't free the sve_state. Signed-off-by: Masayoshi Mizuma Reported-by: Hidetoshi Seto --- arch/arm64/include/asm/processor.h | 1 + arch/arm64/kernel/fpsimd.c | 6 ++++-- arch/arm64/kernel/process.c | 2 ++ 3 files changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 5623685c7d13..3ca3e350145a 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -143,6 +143,7 @@ struct thread_struct { unsigned long fault_address; /* fault info */ unsigned long fault_code; /* ESR_EL1 value */ struct debug_info debug; /* debugging */ + unsigned int fork_in_progress; #ifdef CONFIG_ARM64_PTR_AUTH struct ptrauth_keys keys_user; #endif diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 37d3912cfe06..8641db4cb062 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -202,8 +202,10 @@ static bool have_cpu_fpsimd_context(void) */ static void __sve_free(struct task_struct *task) { - kfree(task->thread.sve_state); - task->thread.sve_state = NULL; + if (!task->thread.fork_in_progress) { + kfree(task->thread.sve_state); + task->thread.sve_state = NULL; + } } static void sve_free(struct task_struct *task) diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index a47462def04b..8ac0ee4e5f76 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -347,6 +347,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) if (current->mm) fpsimd_preserve_current_state(); *dst = *src; + dst->thread.fork_in_progress = 1; return 0; } @@ -365,6 +366,7 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start, * and disable discard SVE state for p: */ clear_tsk_thread_flag(p, TIF_SVE); + p->thread.fork_in_progress = 0; p->thread.sve_state = NULL; /* -- 2.18.1