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Date:   Thu, 5 Apr 2018 21:26:51 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Michal Hocko <mhocko@...nel.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: [PATCH v2] prctl: Deprecate non PR_SET_MM_MAP operations

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.

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>
---
 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

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