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hugetlbfs: check for pgoff value overflow

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A vma with vm_pgoff large enough to overflow a loff_t type when
converted to a byte offset can be passed via the remap_file_pages system
call.  The hugetlbfs mmap routine uses the byte offset to calculate
reservations and file size.

A sequence such as:

  mmap(0x20a00000, 0x600000, 0, 0x66033, -1, 0);
  remap_file_pages(0x20a00000, 0x600000, 0, 0x20000000000000, 0);

will result in the following when task exits/file closed,

  kernel BUG at mm/hugetlb.c:749!
  Call Trace:
    hugetlbfs_evict_inode+0x2f/0x40
    evict+0xcb/0x190
    __dentry_kill+0xcb/0x150
    __fput+0x164/0x1e0
    task_work_run+0x84/0xa0
    exit_to_usermode_loop+0x7d/0x80
    do_syscall_64+0x18b/0x190
    entry_SYSCALL_64_after_hwframe+0x3d/0xa2

The overflowed pgoff value causes hugetlbfs to try to set up a mapping
with a negative range (end < start) that leaves invalid state which
causes the BUG.

The previous overflow fix to this code was incomplete and did not take
the remap_file_pages system call into account.

[mike.kravetz@oracle.com: v3]
  Link: http://lkml.kernel.org/r/20180309002726.7248-1-mike.kravetz@oracle.com
[akpm@linux-foundation.org: include mmdebug.h]
[akpm@linux-foundation.org: fix -ve left shift count on sh]
Link: http://lkml.kernel.org/r/20180308210502.15952-1-mike.kravetz@oracle.com
Fixes: 045c7a3f53 ("hugetlbfs: fix offset overflow in hugetlbfs mmap")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reported-by: Nic Losby <blurbdust@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Yisheng Xie <xieyisheng1@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mike Kravetz
2018-03-22 16:17:13 -07:00
committed by Linus Torvalds
parent 2e517d6816
commit 63489f8e82
2 changed files with 21 additions and 3 deletions
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7
mm/hugetlb.c
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@@ -18,6 +18,7 @@
#include <linux/bootmem.h>
#include <linux/sysfs.h>
#include <linux/slab.h>
#include <linux/mmdebug.h>
#include <linux/sched/signal.h>
#include <linux/rmap.h>
#include <linux/string_helpers.h>
@@ -4374,6 +4375,12 @@ int hugetlb_reserve_pages(struct inode *inode,
struct resv_map *resv_map;
long gbl_reserve;
/* This should never happen */
if (from > to) {
VM_WARN(1, "%s called with a negative range\n", __func__);
return -EINVAL;
}
/*
* Only apply hugepage reservation if asked. At fault time, an
* attempt will be made for VM_NORESERVE to allocate a page