linux-kernel - Re: [PATCH v2] prctl: fix compat handling for prctl

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Date:   Wed, 18 Apr 2018 21:35:58 -0400
From:   Andy Lutomirski <luto@...capital.net>
To:     Li Bin <huawei.libin@...wei.com>
Cc:     Al Viro <viro@...IV.linux.org.uk>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        linux-kernel@...r.kernel.org, guohanjun@...wei.com
Subject: Re: [PATCH v2] prctl: fix compat handling for prctl



> On Apr 18, 2018, at 9:06 PM, Li Bin <huawei.libin@...wei.com> wrote:
> 
> The member auxv in prctl_mm_map structure which be shared with
> userspace is pointer type, but the kernel supporting COMPAT didn't
> handle it. This patch fix the compat handling for prctl syscall.
> 
> Signed-off-by: Li Bin <huawei.libin@...wei.com>
> ---
> kernel/sys.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 42 insertions(+)
> 
> diff --git a/kernel/sys.c b/kernel/sys.c
> index ad69218..d4259938 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1969,6 +1969,26 @@ static int validate_prctl_map(struct prctl_mm_map *prctl_map)
> }
> 
> #ifdef CONFIG_CHECKPOINT_RESTORE
> +
> +#ifdef CONFIG_COMPAT
> +struct compat_prctl_mm_map {
> +    __u64   start_code;     /* code section bounds */
> +    __u64   end_code;
> +    __u64   start_data;     /* data section bounds */
> +    __u64   end_data;
> +    __u64   start_brk;      /* heap for brk() syscall */
> +    __u64   brk;
> +    __u64   start_stack;        /* stack starts at */
> +    __u64   arg_start;      /* command line arguments bounds */
> +    __u64   arg_end;
> +    __u64   env_start;      /* environment variables bounds */
> +    __u64   env_end;
> +    compat_uptr_t   auxv;   /* auxiliary vector */
> +    __u32   auxv_size;      /* vector size */
> +    __u32   exe_fd;         /* /proc/$pid/exe link file */
> +};
> +#endif
> +
> static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data_size)
> {
>    struct prctl_mm_map prctl_map = { .exe_fd = (u32)-1, };
> @@ -1986,6 +2006,28 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data
>    if (data_size != sizeof(prctl_map))
>        return -EINVAL;
> 
> +#ifdef CONFIG_COMPAT
> +    if (in_compat_syscall()) {
> +        struct compat_prctl_mm_map prctl_map32;
> +        if (copy_from_user(&prctl_map32, addr, sizeof(prctl_map32)))
> +            return -EFAULT;
> +
> +        prctl_map.start_code = prctl_map32.start_code;
> +        prctl_map.end_code = prctl_map32.end_code;
> +        prctl_map.start_data = prctl_map32.start_data;
> +        prctl_map.end_data = prctl_map32.end_data;
> +        prctl_map.start_brk = prctl_map32.start_brk;
> +        prctl_map.brk = prctl_map32.brk;
> +        prctl_map.start_stack = prctl_map32.start_stack;
> +        prctl_map.arg_start = prctl_map32.arg_start;
> +        prctl_map.arg_end = prctl_map32.arg_end;
> +        prctl_map.env_start = prctl_map32.env_start;
> +        prctl_map.env_end = prctl_map32.env_end;
> +        prctl_map.auxv = compat_ptr(prctl_map32.auxv);
> +        prctl_map.auxv_size = prctl_map32.auxv_size;
> +        prctl_map.exe_fd = prctl_map32.exe_fd;
> +    } else
> +#endif
>    if (copy_from_user(&prctl_map, addr, sizeof(prctl_map)))
>        return -EFAULT;
> 
> -- 
> 1.7.12.4
>