commit cf089c4da08614410c789fb61af3b712c3bd1850
author Shubhraprakash Das <sadas@codeaurora.org> Thu Dec 22 14:28:07 2011 -0700
committer Shubhraprakash Das <sadas@codeaurora.org> Fri Jan 20 12:26:47 2012 -0700
tree 0d93ade65db98b376e5bd84adae97f93ef7615c5
parent 1aa4848c00a370a2d7cf5d779da055fce19f037d

mm: ashmem: Make sure vma is valid while flushing

Ensure that the vma that the ashmem region is tied to
is valid before flushing and hold the mm semaphore so
that the vma does not get destroyed from under while
it's being flushed.

CRs-Fixed: 326685
Change-Id: I86320ffe9e6570e6ffa7dda68ab26be7aed86afd
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>

mm/ashmem.c

diff --git a/mm/ashmem.c b/mm/ashmem.c
index bc977ee..e4aab56 100644
--- a/mm/ashmem.c
+++ b/mm/ashmem.c
@@ -673,10 +673,28 @@
 	void (*cache_func)(unsigned long vstart, unsigned long length,
 				unsigned long pstart))
 {
+	int ret = 0;
+	struct vm_area_struct *vma;
 #ifdef CONFIG_OUTER_CACHE
 	unsigned long vaddr;
 #endif
-	mutex_lock(&ashmem_mutex);
+	if (!asma->vm_start)
+		return -EINVAL;
+
+	down_read(&current->mm->mmap_sem);
+	vma = find_vma(current->mm, asma->vm_start);
+	if (!vma) {
+		ret = -EINVAL;
+		goto done;
+	}
+	if (vma->vm_file != asma->file) {
+		ret = -EINVAL;
+		goto done;
+	}
+	if ((asma->vm_start + asma->size) > (vma->vm_start + vma->vm_end)) {
+		ret = -EINVAL;
+		goto done;
+	}
 #ifndef CONFIG_OUTER_CACHE
 	cache_func(asma->vm_start, asma->size, 0);
 #else
@@ -689,8 +707,11 @@
 		cache_func(vaddr, PAGE_SIZE, physaddr);
 	}
 #endif
-	mutex_unlock(&ashmem_mutex);
-	return 0;
+done:
+	up_read(&current->mm->mmap_sem);
+	if (ret)
+		asma->vm_start = 0;
+	return ret;
 }
 
 static long ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg)