From: Mike Kravetz mike.kravetz@oracle.com Subject: hugetlbfs: check for pgoff value overflow
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: 045c7a3f53d9 ("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 <> ---
fs/hugetlbfs/inode.c | 17 ++++++++++++++--- mm/hugetlb.c | 7 +++++++ 2 files changed, 21 insertions(+), 3 deletions(-)
diff -puN fs/hugetlbfs/inode.c~hugetlbfs-check-for-pgoff-value-overflow fs/hugetlbfs/inode.c --- a/fs/hugetlbfs/inode.c~hugetlbfs-check-for-pgoff-value-overflow +++ a/fs/hugetlbfs/inode.c @@ -108,6 +108,16 @@ static void huge_pagevec_release(struct pagevec_reinit(pvec); }
+/* + * Mask used when checking the page offset value passed in via system + * calls. This value will be converted to a loff_t which is signed. + * Therefore, we want to check the upper PAGE_SHIFT + 1 bits of the + * value. The extra bit (- 1 in the shift value) is to take the sign + * bit into account. + */ +#define PGOFF_LOFFT_MAX \ + (((1UL << (PAGE_SHIFT + 1)) - 1) << (BITS_PER_LONG - (PAGE_SHIFT + 1))) + static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) { struct inode *inode = file_inode(file); @@ -127,12 +137,13 @@ static int hugetlbfs_file_mmap(struct fi vma->vm_ops = &hugetlb_vm_ops;
/* - * Offset passed to mmap (before page shift) could have been - * negative when represented as a (l)off_t. + * page based offset in vm_pgoff could be sufficiently large to + * overflow a (l)off_t when converted to byte offset. */ - if (((loff_t)vma->vm_pgoff << PAGE_SHIFT) < 0) + if (vma->vm_pgoff & PGOFF_LOFFT_MAX) return -EINVAL;
+ /* must be huge page aligned */ if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT)) return -EINVAL;
diff -puN mm/hugetlb.c~hugetlbfs-check-for-pgoff-value-overflow mm/hugetlb.c --- a/mm/hugetlb.c~hugetlbfs-check-for-pgoff-value-overflow +++ a/mm/hugetlb.c @@ -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 * 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 _