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authorRoman Penyaev <rpenyaev@suse.de>2019-03-05 15:43:20 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-03-05 21:07:15 -0800
commit401592d2e095947344e10ec0623adbcd58934dd4 (patch)
tree86306037180380527baee3893d998e585c1e1e7f /mm
parent5a82ac715d1fd4f117d7b7e76664c0ea3d09e5e7 (diff)
mm/vmalloc: fix size check for remap_vmalloc_range_partial()
When VM_NO_GUARD is not set area->size includes adjacent guard page, thus for correct size checking get_vm_area_size() should be used, but not area->size. This fixes possible kernel oops when userspace tries to mmap an area on 1 page bigger than was allocated by vmalloc_user() call: the size check inside remap_vmalloc_range_partial() accounts non-existing guard page also, so check successfully passes but vmalloc_to_page() returns NULL (guard page does not physically exist). The following code pattern example should trigger an oops: static int oops_mmap(struct file *file, struct vm_area_struct *vma) { void *mem; mem = vmalloc_user(4096); BUG_ON(!mem); /* Do not care about mem leak */ return remap_vmalloc_range(vma, mem, 0); } And userspace simply mmaps size + PAGE_SIZE: mmap(NULL, 8192, PROT_WRITE|PROT_READ, MAP_PRIVATE, fd, 0); Possible candidates for oops which do not have any explicit size checks: *** drivers/media/usb/stkwebcam/stk-webcam.c: v4l_stk_mmap[789] ret = remap_vmalloc_range(vma, sbuf->buffer, 0); Or the following one: *** drivers/video/fbdev/core/fbmem.c static int fb_mmap(struct file *file, struct vm_area_struct * vma) ... res = fb->fb_mmap(info, vma); Where fb_mmap callback calls remap_vmalloc_range() directly without any explicit checks: *** drivers/video/fbdev/vfb.c static int vfb_mmap(struct fb_info *info, struct vm_area_struct *vma) { return remap_vmalloc_range(vma, (void *)info->fix.smem_start, vma->vm_pgoff); } Link: http://lkml.kernel.org/r/20190103145954.16942-2-rpenyaev@suse.de Signed-off-by: Roman Penyaev <rpenyaev@suse.de> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Joe Perches <joe@perches.com> Cc: "Luis R. Rodriguez" <mcgrof@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/vmalloc.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index cb827624c006..421ae07ffb37 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2249,7 +2249,7 @@ int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr,
if (!(area->flags & VM_USERMAP))
return -EINVAL;
- if (kaddr + size > area->addr + area->size)
+ if (kaddr + size > area->addr + get_vm_area_size(area))
return -EINVAL;
do {