Hi Mike, On 2018/3/8 7:59, Mike Kravetz wrote: > 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. > > Reported-by: Nic Losby <blurbdust@xxxxxxxxx> > Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > --- > fs/hugetlbfs/inode.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index 8fe1b0aa2896..cb288dec5564 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -127,12 +127,13 @@ 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) > + if (vma->vm_pgoff && ((loff_t)vma->vm_pgoff << PAGE_SHIFT) <= 0) > return -EINVAL; This seems still no the right fix, taking the following case as an example: mmap(0x20a00000, 0x600000, 0, 0x66033, -1, 0); remap_file_pages(0x20a00000, 0x600000, 0, 0x0020001000000000, 0); You should just check the highest PAGE_SHIFT+1 bits of pgoff in you want check at this point, right? However, region_chg makes me a litter puzzle that when its return value < 0, sometime adds_in_progress is added like this case, while sometime it is not. so why not just change at the beginning of region_chg ? if (f > t) return -EINVAL; Thanks Yisheng > > + /* must be huge page aligned */ > if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT)) > return -EINVAL; > >
