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Date: Thu, 5 Apr 2018 20:56:50 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Cyrill Gorcunov <gorcunov@...il.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Randy Dunlap <rdunlap@...radead.org>,
Andrey Vagin <avagin@...nvz.org>,
Andrew Morton <akpm@...uxfoundation.org>,
Pavel Emelyanov <xemul@...tuozzo.com>,
Michael Kerrisk <mtk.manpages@...il.com>,
Yang Shi <yang.shi@...ux.alibaba.com>
Subject: Re: [PATCH v2] prctl: Deprecate non PR_SET_MM_MAP operations
On Thu 05-04-18 21:26:51, Cyrill Gorcunov wrote:
> An ability to manipulate mm_struct fields was introduced in
> sake of CRIU in first place. Later we provide more suitable
> and safe operation PR_SET_MM_MAP where all fields to be modifed
> are passed in one structure which allows us to make more detailed
> verification.
I hope this will serve as a memento for future single-user APIs
proposals. The whole thing was a bad idea since the beginning.
> Still old interface remains present for compatibility reason
> though CRIU itself already switched to PR_SET_MM_MAP on its
> own long ago.
>
> Googling didn't reveal some other users of this operation
> so I think it should be safe to remove this interface.
>
> v2:
> - Improve warning message
> - Drop redundant args check
>
> CC: Andrey Vagin <avagin@...nvz.org>
> CC: Andrew Morton <akpm@...uxfoundation.org>
> CC: Pavel Emelyanov <xemul@...tuozzo.com>
> CC: Michael Kerrisk <mtk.manpages@...il.com>
> CC: Yang Shi <yang.shi@...ux.alibaba.com>
> CC: Michal Hocko <mhocko@...nel.org>
> Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
Acked-by: Michal Hocko <mhocko@...e.com>
and fingers crossed that we haven't grown other users outside of CRIU
which is quite bound to specific kernels AFAIK.
> ---
> kernel/sys.c | 151 -----------------------------------------------------------
> 1 file changed, 2 insertions(+), 149 deletions(-)
>
> Index: linux-ml.git/kernel/sys.c
> ===================================================================
> --- linux-ml.git.orig/kernel/sys.c
> +++ linux-ml.git/kernel/sys.c
> @@ -2053,163 +2053,16 @@ static int prctl_set_mm_map(int opt, con
> }
> #endif /* CONFIG_CHECKPOINT_RESTORE */
>
> -static int prctl_set_auxv(struct mm_struct *mm, unsigned long addr,
> - unsigned long len)
> -{
> - /*
> - * This doesn't move the auxiliary vector itself since it's pinned to
> - * mm_struct, but it permits filling the vector with new values. It's
> - * up to the caller to provide sane values here, otherwise userspace
> - * tools which use this vector might be unhappy.
> - */
> - unsigned long user_auxv[AT_VECTOR_SIZE];
> -
> - if (len > sizeof(user_auxv))
> - return -EINVAL;
> -
> - if (copy_from_user(user_auxv, (const void __user *)addr, len))
> - return -EFAULT;
> -
> - /* Make sure the last entry is always AT_NULL */
> - user_auxv[AT_VECTOR_SIZE - 2] = 0;
> - user_auxv[AT_VECTOR_SIZE - 1] = 0;
> -
> - BUILD_BUG_ON(sizeof(user_auxv) != sizeof(mm->saved_auxv));
> -
> - task_lock(current);
> - memcpy(mm->saved_auxv, user_auxv, len);
> - task_unlock(current);
> -
> - return 0;
> -}
> -
> static int prctl_set_mm(int opt, unsigned long addr,
> unsigned long arg4, unsigned long arg5)
> {
> - struct mm_struct *mm = current->mm;
> - struct prctl_mm_map prctl_map;
> - struct vm_area_struct *vma;
> - int error;
> -
> - if (arg5 || (arg4 && (opt != PR_SET_MM_AUXV &&
> - opt != PR_SET_MM_MAP &&
> - opt != PR_SET_MM_MAP_SIZE)))
> - return -EINVAL;
> -
> #ifdef CONFIG_CHECKPOINT_RESTORE
> if (opt == PR_SET_MM_MAP || opt == PR_SET_MM_MAP_SIZE)
> return prctl_set_mm_map(opt, (const void __user *)addr, arg4);
> #endif
>
> - if (!capable(CAP_SYS_RESOURCE))
> - return -EPERM;
> -
> - if (opt == PR_SET_MM_EXE_FILE)
> - return prctl_set_mm_exe_file(mm, (unsigned int)addr);
> -
> - if (opt == PR_SET_MM_AUXV)
> - return prctl_set_auxv(mm, addr, arg4);
> -
> - if (addr >= TASK_SIZE || addr < mmap_min_addr)
> - return -EINVAL;
> -
> - error = -EINVAL;
> -
> - down_write(&mm->mmap_sem);
> - vma = find_vma(mm, addr);
> -
> - prctl_map.start_code = mm->start_code;
> - prctl_map.end_code = mm->end_code;
> - prctl_map.start_data = mm->start_data;
> - prctl_map.end_data = mm->end_data;
> - prctl_map.start_brk = mm->start_brk;
> - prctl_map.brk = mm->brk;
> - prctl_map.start_stack = mm->start_stack;
> - prctl_map.arg_start = mm->arg_start;
> - prctl_map.arg_end = mm->arg_end;
> - prctl_map.env_start = mm->env_start;
> - prctl_map.env_end = mm->env_end;
> - prctl_map.auxv = NULL;
> - prctl_map.auxv_size = 0;
> - prctl_map.exe_fd = -1;
> -
> - switch (opt) {
> - case PR_SET_MM_START_CODE:
> - prctl_map.start_code = addr;
> - break;
> - case PR_SET_MM_END_CODE:
> - prctl_map.end_code = addr;
> - break;
> - case PR_SET_MM_START_DATA:
> - prctl_map.start_data = addr;
> - break;
> - case PR_SET_MM_END_DATA:
> - prctl_map.end_data = addr;
> - break;
> - case PR_SET_MM_START_STACK:
> - prctl_map.start_stack = addr;
> - break;
> - case PR_SET_MM_START_BRK:
> - prctl_map.start_brk = addr;
> - break;
> - case PR_SET_MM_BRK:
> - prctl_map.brk = addr;
> - break;
> - case PR_SET_MM_ARG_START:
> - prctl_map.arg_start = addr;
> - break;
> - case PR_SET_MM_ARG_END:
> - prctl_map.arg_end = addr;
> - break;
> - case PR_SET_MM_ENV_START:
> - prctl_map.env_start = addr;
> - break;
> - case PR_SET_MM_ENV_END:
> - prctl_map.env_end = addr;
> - break;
> - default:
> - goto out;
> - }
> -
> - error = validate_prctl_map(&prctl_map);
> - if (error)
> - goto out;
> -
> - switch (opt) {
> - /*
> - * If command line arguments and environment
> - * are placed somewhere else on stack, we can
> - * set them up here, ARG_START/END to setup
> - * command line argumets and ENV_START/END
> - * for environment.
> - */
> - case PR_SET_MM_START_STACK:
> - case PR_SET_MM_ARG_START:
> - case PR_SET_MM_ARG_END:
> - case PR_SET_MM_ENV_START:
> - case PR_SET_MM_ENV_END:
> - if (!vma) {
> - error = -EFAULT;
> - goto out;
> - }
> - }
> -
> - mm->start_code = prctl_map.start_code;
> - mm->end_code = prctl_map.end_code;
> - mm->start_data = prctl_map.start_data;
> - mm->end_data = prctl_map.end_data;
> - mm->start_brk = prctl_map.start_brk;
> - mm->brk = prctl_map.brk;
> - mm->start_stack = prctl_map.start_stack;
> - mm->arg_start = prctl_map.arg_start;
> - mm->arg_end = prctl_map.arg_end;
> - mm->env_start = prctl_map.env_start;
> - mm->env_end = prctl_map.env_end;
> -
> - error = 0;
> -out:
> - up_write(&mm->mmap_sem);
> - return error;
> + pr_warn_once("PR_SET_MM_* has been removed. Use PR_SET_MM_MAP instead\n");
> + return -EINVAL;
> }
>
> #ifdef CONFIG_CHECKPOINT_RESTORE
--
Michal Hocko
SUSE Labs
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