[PATCH] unshare system call -v5: unshare vm

If vm structure is being shared, allocate a new one and copy information from the current, shared, structure. Signed-off-by: Janak Desai <janak@us.ibm.com> Cc: Al Viro <viro@ftp.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Andi Kleen <ak@muc.de> Cc: Paul Mackerras <paulus@samba.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] unshare system call -v5: unshare vm
If vm structure is being shared, allocate a new one and copy information from the current, shared, structure. Signed-off-by: Janak Desai <janak@us.ibm.com> Cc: Al Viro <viro@ftp.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Andi Kleen <ak@muc.de> Cc: Paul Mackerras <paulus@samba.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
JANAK DESAI · Linus Torvalds
1 parent 741a295130
Showing 1 changed file with 56 additions and 31 deletions Side-by-side Diff
kernel/fork.c
@@ -446,6 +446,55 @@
 	}
 }
  
+/*
+ * Allocate a new mm structure and copy contents from the
+ * mm structure of the passed in task structure.
+ */
+static struct mm_struct *dup_mm(struct task_struct *tsk)
+{
+	struct mm_struct *mm, *oldmm = current->mm;
+	int err;
+
+	if (!oldmm)
+		return NULL;
+
+	mm = allocate_mm();
+	if (!mm)
+		goto fail_nomem;
+
+	memcpy(mm, oldmm, sizeof(*mm));
+
+	if (!mm_init(mm))
+		goto fail_nomem;
+
+	if (init_new_context(tsk, mm))
+		goto fail_nocontext;
+
+	err = dup_mmap(mm, oldmm);
+	if (err)
+		goto free_pt;
+
+	mm->hiwater_rss = get_mm_rss(mm);
+	mm->hiwater_vm = mm->total_vm;
+
+	return mm;
+
+free_pt:
+	mmput(mm);
+
+fail_nomem:
+	return NULL;
+
+fail_nocontext:
+	/*
+	 * If init_new_context() failed, we cannot use mmput() to free the mm
+	 * because it calls destroy_context()
+	 */
+	mm_free_pgd(mm);
+	free_mm(mm);
+	return NULL;
+}
+
 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 {
 	struct mm_struct * mm, *oldmm;
  
  
  
@@ -473,43 +522,17 @@
 	}
  
 	retval = -ENOMEM;
-	mm = allocate_mm();
+	mm = dup_mm(tsk);
 	if (!mm)
 		goto fail_nomem;
  
-	/* Copy the current MM stuff.. */
-	memcpy(mm, oldmm, sizeof(*mm));
-	if (!mm_init(mm))
-		goto fail_nomem;
-
-	if (init_new_context(tsk,mm))
-		goto fail_nocontext;
-
-	retval = dup_mmap(mm, oldmm);
-	if (retval)
-		goto free_pt;
-
-	mm->hiwater_rss = get_mm_rss(mm);
-	mm->hiwater_vm = mm->total_vm;
-
 good_mm:
 	tsk->mm = mm;
 	tsk->active_mm = mm;
 	return 0;
  
-free_pt:
-	mmput(mm);
 fail_nomem:
 	return retval;
-
-fail_nocontext:
-	/*
-	 * If init_new_context() failed, we cannot use mmput() to free the mm
-	 * because it calls destroy_context()
-	 */
-	mm_free_pgd(mm);
-	free_mm(mm);
-	return retval;
 }
  
 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
  
  
@@ -1423,18 +1446,20 @@
 }
  
 /*
- * Unsharing of vm for tasks created with CLONE_VM is not supported yet
+ * Unshare vm if it is being shared
  */
 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
 {
 	struct mm_struct *mm = current->mm;
  
 	if ((unshare_flags & CLONE_VM) &&
-	    (mm && atomic_read(&mm->mm_users) > 1))
-		return -EINVAL;
+	    (mm && atomic_read(&mm->mm_users) > 1)) {
+		*new_mmp = dup_mm(current);
+		if (!*new_mmp)
+			return -ENOMEM;
+	}
  
 	return 0;
-
 }
  
 /*
...	...	@@ -446,6 +446,55 @@
446	446	}
447	447	}
448	448
	449	+/*
	450	+ * Allocate a new mm structure and copy contents from the
	451	+ * mm structure of the passed in task structure.
	452	+ */
	453	+static struct mm_struct dup_mm(struct task_struct tsk)
	454	+{
	455	+ struct mm_struct mm, oldmm = current->mm;
	456	+ int err;
	457	+
	458	+ if (!oldmm)
	459	+ return NULL;
	460	+
	461	+ mm = allocate_mm();
	462	+ if (!mm)
	463	+ goto fail_nomem;
	464	+
	465	+ memcpy(mm, oldmm, sizeof(*mm));
	466	+
	467	+ if (!mm_init(mm))
	468	+ goto fail_nomem;
	469	+
	470	+ if (init_new_context(tsk, mm))
	471	+ goto fail_nocontext;
	472	+
	473	+ err = dup_mmap(mm, oldmm);
	474	+ if (err)
	475	+ goto free_pt;
	476	+
	477	+ mm->hiwater_rss = get_mm_rss(mm);
	478	+ mm->hiwater_vm = mm->total_vm;
	479	+
	480	+ return mm;
	481	+
	482	+free_pt:
	483	+ mmput(mm);
	484	+
	485	+fail_nomem:
	486	+ return NULL;
	487	+
	488	+fail_nocontext:
	489	+ /*
	490	+ * If init_new_context() failed, we cannot use mmput() to free the mm
	491	+ * because it calls destroy_context()
	492	+ */
	493	+ mm_free_pgd(mm);
	494	+ free_mm(mm);
	495	+ return NULL;
	496	+}
	497	+
449	498	static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
450	499	{
451	500	struct mm_struct * mm, *oldmm;
452	501
453	502
454	503
...	...	@@ -473,43 +522,17 @@
473	522	}
474	523
475	524	retval = -ENOMEM;
476		- mm = allocate_mm();
	525	+ mm = dup_mm(tsk);
477	526	if (!mm)
478	527	goto fail_nomem;
479	528
480		- /* Copy the current MM stuff.. */
481		- memcpy(mm, oldmm, sizeof(*mm));
482		- if (!mm_init(mm))
483		- goto fail_nomem;
484		-
485		- if (init_new_context(tsk,mm))
486		- goto fail_nocontext;
487		-
488		- retval = dup_mmap(mm, oldmm);
489		- if (retval)
490		- goto free_pt;
491		-
492		- mm->hiwater_rss = get_mm_rss(mm);
493		- mm->hiwater_vm = mm->total_vm;
494		-
495	529	good_mm:
496	530	tsk->mm = mm;
497	531	tsk->active_mm = mm;
498	532	return 0;
499	533
500		-free_pt:
501		- mmput(mm);
502	534	fail_nomem:
503	535	return retval;
504		-
505		-fail_nocontext:
506		- /*
507		- * If init_new_context() failed, we cannot use mmput() to free the mm
508		- * because it calls destroy_context()
509		- */
510		- mm_free_pgd(mm);
511		- free_mm(mm);
512		- return retval;
513	536	}
514	537
515	538	static inline struct fs_struct __copy_fs_struct(struct fs_struct old)
516	539
517	540
...	...	@@ -1423,18 +1446,20 @@
1423	1446	}
1424	1447
1425	1448	/*
1426		- * Unsharing of vm for tasks created with CLONE_VM is not supported yet
	1449	+ * Unshare vm if it is being shared
1427	1450	*/
1428	1451	static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1429	1452	{
1430	1453	struct mm_struct *mm = current->mm;
1431	1454
1432	1455	if ((unshare_flags & CLONE_VM) &&
1433		- (mm && atomic_read(&mm->mm_users) > 1))
1434		- return -EINVAL;
	1456	+ (mm && atomic_read(&mm->mm_users) > 1)) {
	1457	+ *new_mmp = dup_mm(current);
	1458	+ if (!*new_mmp)
	1459	+ return -ENOMEM;
	1460	+ }
1435	1461
1436	1462	return 0;
1437		-
1438	1463	}
1439	1464
1440	1465	/*