CVE-2013-4511: Numeric Errors (CWE-189)
value: Multiple integer overflows in Alchemy LCD frame-buffer drivers in the Linux kernel before 3.12 allow local users to create a read-write memory mapping for the entirety of kernel memory, and consequently gain privileges, via crafted mmap operations, related to the (1) au1100fb_fb_mmap function in drivers/video/au1100fb.c and the (2) au1200fb_fb_mmap function in drivers/video/au1200fb.c.
CWE description: Weaknesses in this category are related to improper calculation or conversion of numbers.
Published: 2013-11-12T14:35Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: drivers/uio/uio.c, drivers/video/au1100fb.c, drivers/video/au1200fb.c
Commit date: 2013-10-29 10:21:34 -0700
Commit message: Fix a few incorrectly checked [io_]remap_pfn_range() calls

Nico Golde reports a few straggling uses of [io_]remap_pfn_range() that
really should use the vm_iomap_memory() helper.  This trivially converts
two of them to the helper, and comments about why the third one really
needs to continue to use remap_pfn_range(), and adds the missing size
check.

Reported-by: Nico Golde <nico@ngolde.de>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org.

Diff: diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index ba475632c5fa2a..0e808cf91d97e9 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -640,20 +640,33 @@ static const struct vm_operations_struct uio_physical_vm_ops = {
 
 static int uio_mmap_physical(struct vm_area_struct *vma)
 {
 	struct uio_device *idev = vma->vm_private_data;
 	int mi = uio_find_mem_index(vma);
+	struct uio_mem *mem;
 	if (mi < 0)
 		return -EINVAL;
+	mem = idev->info->mem + mi;
 
-	vma->vm_ops = &uio_physical_vm_ops;
+	if (vma->vm_end - vma->vm_start > mem->size)
+		return -EINVAL;
 
+	vma->vm_ops = &uio_physical_vm_ops;
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 
+	/*
+	 * We cannot use the vm_iomap_memory() helper here,
+	 * because vma->vm_pgoff is the map index we looked
+	 * up above in uio_find_mem_index(), rather than an
+	 * actual page offset into the mmap.
+	 *
+	 * So we just do the physical mmap without a page
+	 * offset.
+	 */
 	return remap_pfn_range(vma,
 			       vma->vm_start,
-			       idev->info->mem[mi].addr >> PAGE_SHIFT,
+			       mem->addr >> PAGE_SHIFT,
 			       vma->vm_end - vma->vm_start,
 			       vma->vm_page_prot);
 }
 
 static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
diff --git a/drivers/video/au1100fb.c b/drivers/video/au1100fb.c
index a54ccdc4d6618b..22ad85242e5b92 100644
--- a/drivers/video/au1100fb.c
+++ b/drivers/video/au1100fb.c
@@ -359,41 +359,17 @@ void au1100fb_fb_rotate(struct fb_info *fbi, int angle)
  * to allow the use of the TLB streaming flag (CCA=6)
  */
 int au1100fb_fb_mmap(struct fb_info *fbi, struct vm_area_struct *vma)
 {
 	struct au1100fb_device *fbdev;
-	unsigned int len;
-	unsigned long start=0, off;
 
 	fbdev = to_au1100fb_device(fbi);
 
-	if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT)) {
-		return -EINVAL;
-	}
-
-	start = fbdev->fb_phys & PAGE_MASK;
-	len = PAGE_ALIGN((start & ~PAGE_MASK) + fbdev->fb_len);
-
-	off = vma->vm_pgoff << PAGE_SHIFT;
-
-	if ((vma->vm_end - vma->vm_start + off) > len) {
-		return -EINVAL;
-	}
-
-	off += start;
-	vma->vm_pgoff = off >> PAGE_SHIFT;
-
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 	pgprot_val(vma->vm_page_prot) |= (6 << 9); //CCA=6
 
-	if (io_remap_pfn_range(vma, vma->vm_start, off >> PAGE_SHIFT,
-				vma->vm_end - vma->vm_start,
-				vma->vm_page_prot)) {
-		return -EAGAIN;
-	}
-
-	return 0;
+	return vm_iomap_memory(vma, fbdev->fb_phys, fbdev->fb_len);
 }
 
 static struct fb_ops au1100fb_ops =
 {
 	.owner			= THIS_MODULE,
diff --git a/drivers/video/au1200fb.c b/drivers/video/au1200fb.c
index 301224ecc95071..1d02897d17f27e 100644
--- a/drivers/video/au1200fb.c
+++ b/drivers/video/au1200fb.c
@@ -1231,38 +1231,17 @@ static int au1200fb_fb_blank(int blank_mode, struct fb_info *fbi)
 /* fb_mmap
  * Map video memory in user space. We don't use the generic fb_mmap
  * method mainly to allow the use of the TLB streaming flag (CCA=6)
  */
 static int au1200fb_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
-
 {
-	unsigned int len;
-	unsigned long start=0, off;
 	struct au1200fb_device *fbdev = info->par;
 
-	if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT)) {
-		return -EINVAL;
-	}
-
-	start = fbdev->fb_phys & PAGE_MASK;
-	len = PAGE_ALIGN((start & ~PAGE_MASK) + fbdev->fb_len);
-
-	off = vma->vm_pgoff << PAGE_SHIFT;
-
-	if ((vma->vm_end - vma->vm_start + off) > len) {
-		return -EINVAL;
-	}
-
-	off += start;
-	vma->vm_pgoff = off >> PAGE_SHIFT;
-
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 	pgprot_val(vma->vm_page_prot) |= _CACHE_MASK; /* CCA=7 */
 
-	return io_remap_pfn_range(vma, vma->vm_start, off >> PAGE_SHIFT,
-				  vma->vm_end - vma->vm_start,
-				  vma->vm_page_prot);
+	return vm_iomap_memory(vma, fbdev->fb_phys, fbdev->fb_len);
 }
 
 static void set_global(u_int cmd, struct au1200_lcd_global_regs_t *pdata)
 {
 

Vulnerable code: 	vma->vm_ops = &uio_physical_vm_ops;
			       idev->info->mem[mi].addr >> PAGE_SHIFT,
	unsigned int len;
	unsigned long start=0, off;
	if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT)) {
		return -EINVAL;
	}

	start = fbdev->fb_phys & PAGE_MASK;
	len = PAGE_ALIGN((start & ~PAGE_MASK) + fbdev->fb_len);

	off = vma->vm_pgoff << PAGE_SHIFT;

	if ((vma->vm_end - vma->vm_start + off) > len) {
		return -EINVAL;
	}

	off += start;
	vma->vm_pgoff = off >> PAGE_SHIFT;

	if (io_remap_pfn_range(vma, vma->vm_start, off >> PAGE_SHIFT,
				vma->vm_end - vma->vm_start,
				vma->vm_page_prot)) {
		return -EAGAIN;
	}

	return 0;

	unsigned int len;
	unsigned long start=0, off;
	if (vma->vm_pgoff > (~0UL >> PAGE_SHIFT)) {
		return -EINVAL;
	}

	start = fbdev->fb_phys & PAGE_MASK;
	len = PAGE_ALIGN((start & ~PAGE_MASK) + fbdev->fb_len);

	off = vma->vm_pgoff << PAGE_SHIFT;

	if ((vma->vm_end - vma->vm_start + off) > len) {
		return -EINVAL;
	}

	off += start;
	vma->vm_pgoff = off >> PAGE_SHIFT;

	return io_remap_pfn_range(vma, vma->vm_start, off >> PAGE_SHIFT,
				  vma->vm_end - vma->vm_start,
				  vma->vm_page_prot);
Fixed code: 	struct uio_mem *mem;
	mem = idev->info->mem + mi;
	if (vma->vm_end - vma->vm_start > mem->size)
		return -EINVAL;
	vma->vm_ops = &uio_physical_vm_ops;
	/*
	 * We cannot use the vm_iomap_memory() helper here,
	 * because vma->vm_pgoff is the map index we looked
	 * up above in uio_find_mem_index(), rather than an
	 * actual page offset into the mmap.
	 *
	 * So we just do the physical mmap without a page
	 * offset.
	 */
			       mem->addr >> PAGE_SHIFT,
	return vm_iomap_memory(vma, fbdev->fb_phys, fbdev->fb_len);
	return vm_iomap_memory(vma, fbdev->fb_phys, fbdev->fb_len);