The patch titled Subject: hugetlbfs: check for pgoff value overflow has been added to the -mm tree. Its filename is hugetlbfs-check-for-pgoff-value-overflow.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/hugetlbfs-check-for-pgoff-value-overflow.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/hugetlbfs-check-for-pgoff-value-overflow.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Mike Kravetz <mike.kravetz@xxxxxxxxxx> 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. Link: http://lkml.kernel.org/r/20180308210502.15952-1-mike.kravetz@xxxxxxxxxx Fixes: 045c7a3f53d9 ("hugetlbfs: fix offset overflow in hugetlbfs mmap") Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Reported-by: Nic Losby <blurbdust@xxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Yisheng Xie <xieyisheng1@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- 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 @@ -111,6 +111,7 @@ static void huge_pagevec_release(struct static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) { struct inode *inode = file_inode(file); + unsigned long ovfl_mask; loff_t len, vma_len; int ret; struct hstate *h = hstate_file(file); @@ -127,12 +128,16 @@ 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) + ovfl_mask = (1UL << (PAGE_SHIFT + 1)) - 1; + ovfl_mask <<= ((sizeof(unsigned long) * BITS_PER_BYTE) - + (PAGE_SHIFT + 1)); + if (vma->vm_pgoff & ovfl_mask) 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 @@ -4374,6 +4374,12 @@ 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 _ Patches currently in -mm which might be from mike.kravetz@xxxxxxxxxx are hugetlbfs-check-for-pgoff-value-overflow.patch hugetlbfs-check-for-pgoff-value-overflow-v3.patch mm-hugetlbfs-move-hugetlbfs_i-outside-ifdef-config_hugetlbfs.patch mm-memfd-split-out-memfd-for-use-by-multiple-filesystems.patch mm-memfd-remove-memfd-code-from-shmem-files-and-use-new-memfd-files.patch