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.
Fixes: 045c7a3f53d9 ("hugetlbfs: fix offset overflow in hugetlbfs mmap") Cc: stable@vger.kernel.org Reported-by: Nic Losby blurbdust@gmail.com Signed-off-by: Mike Kravetz mike.kravetz@oracle.com --- Changes in v2 * Use bitmask for overflow check as suggested by Yisheng Xie * Add explicit (from > to) check when setting up reservations * Cc stable
fs/hugetlbfs/inode.c | 11 ++++++++--- mm/hugetlb.c | 6 ++++++ 2 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 8fe1b0aa2896..dafffa6affae 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -111,6 +111,7 @@ static void huge_pagevec_release(struct pagevec *pvec) 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 file *file, struct vm_area_struct *vma) 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 --git a/mm/hugetlb.c b/mm/hugetlb.c index 7c204e3d132b..8eeade0a0b7a 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4374,6 +4374,12 @@ 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