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author | Roman Penyaev <rpenyaev@suse.de> | 2019-03-05 15:43:20 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-03-05 21:07:15 -0800 |
commit | 401592d2e095947344e10ec0623adbcd58934dd4 (patch) | |
tree | 86306037180380527baee3893d998e585c1e1e7f /mm/vmalloc.c | |
parent | 5a82ac715d1fd4f117d7b7e76664c0ea3d09e5e7 (diff) | |
download | linux-stable-401592d2e095947344e10ec0623adbcd58934dd4.tar.gz linux-stable-401592d2e095947344e10ec0623adbcd58934dd4.tar.bz2 linux-stable-401592d2e095947344e10ec0623adbcd58934dd4.zip |
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/vmalloc.c')
-rw-r--r-- | mm/vmalloc.c | 2 |
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 { |