1 From 401592d2e095947344e10ec0623adbcd58934dd4 Mon Sep 17 00:00:00 2001
2 From: Roman Penyaev <rpenyaev@suse.de>
3 Date: Tue, 5 Mar 2019 15:43:20 -0800
4 Subject: mm/vmalloc: fix size check for remap_vmalloc_range_partial()
6 From: Roman Penyaev <rpenyaev@suse.de>
8 commit 401592d2e095947344e10ec0623adbcd58934dd4 upstream.
10 When VM_NO_GUARD is not set area->size includes adjacent guard page,
11 thus for correct size checking get_vm_area_size() should be used, but
14 This fixes possible kernel oops when userspace tries to mmap an area on
15 1 page bigger than was allocated by vmalloc_user() call: the size check
16 inside remap_vmalloc_range_partial() accounts non-existing guard page
17 also, so check successfully passes but vmalloc_to_page() returns NULL
18 (guard page does not physically exist).
20 The following code pattern example should trigger an oops:
22 static int oops_mmap(struct file *file, struct vm_area_struct *vma)
26 mem = vmalloc_user(4096);
28 /* Do not care about mem leak */
30 return remap_vmalloc_range(vma, mem, 0);
33 And userspace simply mmaps size + PAGE_SIZE:
35 mmap(NULL, 8192, PROT_WRITE|PROT_READ, MAP_PRIVATE, fd, 0);
37 Possible candidates for oops which do not have any explicit size
40 *** drivers/media/usb/stkwebcam/stk-webcam.c:
41 v4l_stk_mmap[789] ret = remap_vmalloc_range(vma, sbuf->buffer, 0);
45 *** drivers/video/fbdev/core/fbmem.c
47 fb_mmap(struct file *file, struct vm_area_struct * vma)
49 res = fb->fb_mmap(info, vma);
51 Where fb_mmap callback calls remap_vmalloc_range() directly without any
54 *** drivers/video/fbdev/vfb.c
55 static int vfb_mmap(struct fb_info *info,
56 struct vm_area_struct *vma)
58 return remap_vmalloc_range(vma, (void *)info->fix.smem_start, vma->vm_pgoff);
61 Link: http://lkml.kernel.org/r/20190103145954.16942-2-rpenyaev@suse.de
62 Signed-off-by: Roman Penyaev <rpenyaev@suse.de>
63 Acked-by: Michal Hocko <mhocko@suse.com>
64 Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
65 Cc: Joe Perches <joe@perches.com>
66 Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
67 Cc: <stable@vger.kernel.org>
68 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
69 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
70 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
74 1 file changed, 1 insertion(+), 1 deletion(-)
78 @@ -2162,7 +2162,7 @@ int remap_vmalloc_range_partial(struct v
79 if (!(area->flags & VM_USERMAP))
82 - if (kaddr + size > area->addr + area->size)
83 + if (kaddr + size > area->addr + get_vm_area_size(area))