tree 200a77cb088c818a69e05b68b28a3e582fa3a40c
parent f729c8c9b24f0540a6e6b86e68f3888ba90ef7e7
author Michal Hocko <mhocko@suse.com> 1484096247 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1484101914 -0800

mm, slab: make sure that KMALLOC_MAX_SIZE will fit into MAX_ORDER

Andrey Konovalov has reported the following warning triggered by the
syzkaller fuzzer.

  WARNING: CPU: 1 PID: 9935 at mm/page_alloc.c:3511 __alloc_pages_nodemask+0x159c/0x1e20
  Kernel panic - not syncing: panic_on_warn set ...
  CPU: 1 PID: 9935 Comm: syz-executor0 Not tainted 4.9.0-rc7+ #34
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Call Trace:
    __alloc_pages_slowpath mm/page_alloc.c:3511
    __alloc_pages_nodemask+0x159c/0x1e20 mm/page_alloc.c:3781
    alloc_pages_current+0x1c7/0x6b0 mm/mempolicy.c:2072
    alloc_pages include/linux/gfp.h:469
    kmalloc_order+0x1f/0x70 mm/slab_common.c:1015
    kmalloc_order_trace+0x1f/0x160 mm/slab_common.c:1026
    kmalloc_large include/linux/slab.h:422
    __kmalloc+0x210/0x2d0 mm/slub.c:3723
    kmalloc include/linux/slab.h:495
    ep_write_iter+0x167/0xb50 drivers/usb/gadget/legacy/inode.c:664
    new_sync_write fs/read_write.c:499
    __vfs_write+0x483/0x760 fs/read_write.c:512
    vfs_write+0x170/0x4e0 fs/read_write.c:560
    SYSC_write fs/read_write.c:607
    SyS_write+0xfb/0x230 fs/read_write.c:599
    entry_SYSCALL_64_fastpath+0x1f/0xc2

The issue is caused by a lack of size check for the request size in
ep_write_iter which should be fixed.  It, however, points to another
problem, that SLUB defines KMALLOC_MAX_SIZE too large because the its
KMALLOC_SHIFT_MAX is (MAX_ORDER + PAGE_SHIFT) which means that the
resulting page allocator request might be MAX_ORDER which is too large
(see __alloc_pages_slowpath).

The same applies to the SLOB allocator which allows even larger sizes.
Make sure that they are capped properly and never request more than
MAX_ORDER order.

Link: http://lkml.kernel.org/r/20161220130659.16461-2-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>