The patch titled Subject: mm/vmalloc: fix size check for remap_vmalloc_range_partial() has been added to the -mm tree. Its filename is mm-vmalloc-fix-size-check-for-remap_vmalloc_range_partial.patch

This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-vmalloc-fix-size-check-for-remap... and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-vmalloc-fix-size-check-for-remap...

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------------------------------------------------------ From: Roman Penyaev rpenyaev@suse.de Subject: 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 ---

--- a/mm/vmalloc.c~mm-vmalloc-fix-size-check-for-remap_vmalloc_range_partial +++ a/mm/vmalloc.c @@ -2248,7 +2248,7 @@ int remap_vmalloc_range_partial(struct v 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 { _

Patches currently in -mm which might be from rpenyaev@suse.de are

epoll-make-sure-all-elements-in-ready-list-are-in-fifo-order.patch epoll-loosen-irq-safety-in-ep_poll_callback.patch epoll-unify-awaking-of-wakeup-source-on-ep_poll_callback-path.patch epoll-use-rwlock-in-order-to-reduce-ep_poll_callback-contention.patch mm-vmalloc-fix-size-check-for-remap_vmalloc_range_partial.patch mm-vmalloc-do-not-call-kmemleak_free-on-not-yet-accounted-memory.patch mm-vmalloc-pass-vm_usermap-flags-directly-to-__vmalloc_node_range.patch