linux-kernel - [PATCH 5/5] UML - Fix mm

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Date:	Wed, 6 Feb 2008 12:44:48 -0500
From:	Jeff Dike <jdike@...toit.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	uml-devel <user-mode-linux-devel@...ts.sourceforge.net>,
	Miklos Szeredi <miklos@...redi.hu>
Subject: [PATCH 5/5] UML - Fix mm_context memory leak 

[ Spotted by Miklos ]

Fix a memory leak in init_new_context.  The struct page ** buffer
allocated for install_special_mapping was never recorded, and thus
leaked when the mm_struct was freed.  Fix it by saving the pointer in
mm_context_t and freeing it in arch_exit_mmap.

Signed-off-by: Jeff Dike <jdike@...ux.intel.com>
Cc: Miklos Szeredi <miklos@...redi.hu>
---
 arch/um/include/um_mmu.h  |    1 +
 arch/um/kernel/skas/mmu.c |    5 +++++
 2 files changed, 6 insertions(+)

Index: linux-2.6-git/arch/um/include/um_mmu.h
===================================================================
--- linux-2.6-git.orig/arch/um/include/um_mmu.h	2008-02-06 12:15:05.000000000 -0500
+++ linux-2.6-git/arch/um/include/um_mmu.h	2008-02-06 12:24:08.000000000 -0500
@@ -13,6 +13,7 @@
 typedef struct mm_context {
 	struct mm_id id;
 	struct uml_ldt ldt;
+	struct page **stub_pages;
 } mm_context_t;
 
 extern void __switch_mm(struct mm_id * mm_idp);
Index: linux-2.6-git/arch/um/kernel/skas/mmu.c
===================================================================
--- linux-2.6-git.orig/arch/um/kernel/skas/mmu.c	2008-02-06 12:15:05.000000000 -0500
+++ linux-2.6-git/arch/um/kernel/skas/mmu.c	2008-02-06 12:24:31.000000000 -0500
@@ -91,6 +91,8 @@ int init_new_context(struct task_struct 
 		goto out_free;
 	}
 
+	to_mm->stub_pages = NULL;
+
 	return 0;
 
  out_free:
@@ -126,6 +128,7 @@ void arch_dup_mmap(struct mm_struct *old
 
 	pages[0] = virt_to_page(&__syscall_stub_start);
 	pages[1] = virt_to_page(mm->context.id.stack);
+	mm->context.stub_pages = pages;
 
 	/* dup_mmap already holds mmap_sem */
 	err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
@@ -147,6 +150,8 @@ void arch_exit_mmap(struct mm_struct *mm
 {
 	pte_t *pte;
 
+	if (mm->context.stub_pages != NULL)
+		kfree(mm->context.stub_pages);
 	pte = virt_to_pte(mm, STUB_CODE);
 	if (pte != NULL)
 		pte_clear(mm, STUB_CODE, pte);
--
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