Re: [PATCH v2] prctl: fix compat handling for prctl

From: Andy Lutomirski
Date: Wed Apr 18 2018 - 21:36:05 EST




> On Apr 18, 2018, at 9:06 PM, Li Bin <huawei.libin@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
> 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
>