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@linux.intel.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 6 insertions, 0 deletions

diff --git a/arch/um/include/um_mmu.h b/arch/um/include/um_mmu.h
index 82865fcf6872..f575ff91f2a0 100644
--- a/arch/um/include/um_mmu.h
+++ b/arch/um/include/um_mmu.h
@@ -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);
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index 78b3e9f69d57..0cd9a7a05e77 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -91,6 +91,8 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
                 goto out_free;
         }
 
+        to_mm->stub_pages = NULL;
+
         return 0;
 
  out_free:
@@ -126,6 +128,7 @@ void arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
 
         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);