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From:   Guo Ren <guoren@kernel.org>
Date:   Sat, 12 Oct 2019 09:49:27 +0800
Message-ID: <CAJF2gTTqRhEMhiyTWkj32cboqJoJhte+=9MRV84Pm4w8MVyoRw@mail.gmail.com>
Subject: Re: [PATCH] csky: Initial stack protector support
To:     Mao Han <han_mao@c-sky.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Acked,
I need optimize commit log with:
...

    It's tested with strcpy local array overflow in sys_kill and get:
    stack-protector: Kernel stack is corrupted in: sys_kill+0x23c/0x23c

    TODO:
     - Support task switch for different cannary


On Fri, Oct 11, 2019 at 10:59 AM Mao Han <han_mao@c-sky.com> wrote:
>
> This is a basic -fstack-protector support without per-task canary
> switching. The protector will report something like when stack
> corruption is detected:
>
> stack-protector: Kernel stack is corrupted in: sys_kill+0x23c/0x23c
>
> Tested with a local array overflow in kill system call.
>
> Signed-off-by: Mao Han <han_mao@c-sky.com>
> Cc: Guo Ren <guoren@kernel.org>
> ---
>  arch/csky/Kconfig                      |  1 +
>  arch/csky/include/asm/stackprotector.h | 29 +++++++++++++++++++++++++++++
>  arch/csky/kernel/process.c             |  6 ++++++
>  3 files changed, 36 insertions(+)
>  create mode 100644 arch/csky/include/asm/stackprotector.h
>
> diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
> index 3973847..2852343 100644
> --- a/arch/csky/Kconfig
> +++ b/arch/csky/Kconfig
> @@ -48,6 +48,7 @@ config CSKY
>         select HAVE_PERF_USER_STACK_DUMP
>         select HAVE_DMA_API_DEBUG
>         select HAVE_DMA_CONTIGUOUS
> +       select HAVE_STACKPROTECTOR
>         select HAVE_SYSCALL_TRACEPOINTS
>         select MAY_HAVE_SPARSE_IRQ
>         select MODULES_USE_ELF_RELA if MODULES
> diff --git a/arch/csky/include/asm/stackprotector.h b/arch/csky/include/asm/stackprotector.h
> new file mode 100644
> index 0000000..d7cd4e5
> --- /dev/null
> +++ b/arch/csky/include/asm/stackprotector.h
> @@ -0,0 +1,29 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_STACKPROTECTOR_H
> +#define _ASM_STACKPROTECTOR_H 1
> +
> +#include <linux/random.h>
> +#include <linux/version.h>
> +
> +extern unsigned long __stack_chk_guard;
> +
> +/*
> + * Initialize the stackprotector canary value.
> + *
> + * NOTE: this must only be called from functions that never return,
> + * and it must always be inlined.
> + */
> +static __always_inline void boot_init_stack_canary(void)
> +{
> +       unsigned long canary;
> +
> +       /* Try to get a semi random initial value. */
> +       get_random_bytes(&canary, sizeof(canary));
> +       canary ^= LINUX_VERSION_CODE;
> +       canary &= CANARY_MASK;
> +
> +       current->stack_canary = canary;
> +       __stack_chk_guard = current->stack_canary;
> +}
> +
> +#endif /* __ASM_SH_STACKPROTECTOR_H */
> diff --git a/arch/csky/kernel/process.c b/arch/csky/kernel/process.c
> index f320d92..5349cd8 100644
> --- a/arch/csky/kernel/process.c
> +++ b/arch/csky/kernel/process.c
> @@ -16,6 +16,12 @@
>
>  struct cpuinfo_csky cpu_data[NR_CPUS];
>
> +#ifdef CONFIG_STACKPROTECTOR
> +#include <linux/stackprotector.h>
> +unsigned long __stack_chk_guard __read_mostly;
> +EXPORT_SYMBOL(__stack_chk_guard);
> +#endif
> +
>  asmlinkage void ret_from_fork(void);
>  asmlinkage void ret_from_kernel_thread(void);
>
> --
> 2.7.4
>


-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/