On Wed, Oct 27, 2021 at 1:35 PM Song Liu <songliubraving@xxxxxx> wrote: > > > > > On Oct 27, 2021, at 12:52 PM, Yang Shi <shy828301@xxxxxxxxx> wrote: > > > > The read-only THP for filesystems would collapse THP for file opened > > readonly and mapped with VM_EXEC, the intended usecase is to avoid TLB > > miss for large text segment. But it doesn't restrict the file types so > > THP could be collapsed for non-regular file, for example, block device, > > if it is opened readonly and mapped with EXEC permission. This may > > cause bugs, like [1] and [2]. > > > > This is definitely not intended usecase, so just collapsing THP for regular > > file in order to close the attack surface. > > > > [1] https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@xxxxxxxxxxxxxx/ > > [2] https://lore.kernel.org/linux-mm/000000000000c6a82505ce284e4c@xxxxxxxxxx/ > > > > Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") > > Reported-by: Hao Sun <sunhao.th@xxxxxxxxx> > > Reported-by: syzbot+aae069be1de40fb11825@xxxxxxxxxxxxxxxxxxxxxxxxx > > Cc: Hao Sun <sunhao.th@xxxxxxxxx> > > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > > Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > Cc: Song Liu <songliubraving@xxxxxx> > > Cc: Andrea Righi <andrea.righi@xxxxxxxxxxxxx> > > Cc: <stable@xxxxxxxxxxxxxxx> > > Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> > > Signed-off-by: Yang Shi <shy828301@xxxxxxxxx> > > --- > > The patch is basically based off the proposal from Hugh > > (https://lore.kernel.org/linux-mm/a07564a3-b2fc-9ffe-3ace-3f276075ea5c@xxxxxxxxxx/). > > It seems Hugh is too busy to prepare the patch for formal submission (I > > didn't hear from him by pinging him a couple of times on mailing list), > > so I prepared the patch and added his SOB. > > > > mm/khugepaged.c | 17 ++++++++++------- > > 1 file changed, 10 insertions(+), 7 deletions(-) > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index 045cc579f724..e91b7271275e 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -445,22 +445,25 @@ static bool hugepage_vma_check(struct vm_area_struct *vma, > > if (!transhuge_vma_enabled(vma, vm_flags)) > > return false; > > > > - /* Enabled via shmem mount options or sysfs settings. */ > > - if (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) { > > + if (vma->vm_file) > > return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, > > HPAGE_PMD_NR); > > Am I misreading this? If we return here for vma->vm_file, the following > logic (shmem_file(), etc.) would be skipped, no? Oh, yes, you are right. My mistake. Andrew, Could you please apply the below fix? diff --git a/mm/khugepaged.c b/mm/khugepaged.c index e91b7271275e..26f1798c88d2 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -445,9 +445,9 @@ static bool hugepage_vma_check(struct vm_area_struct *vma, if (!transhuge_vma_enabled(vma, vm_flags)) return false; - if (vma->vm_file) - return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, - HPAGE_PMD_NR); + if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - + vma->vm_pgoff, HPAGE_PMD_NR)) + return false; /* Enabled via shmem mount options or sysfs settings. */ if (shmem_file(vma->vm_file)) > > Thanks, > Song > > > - } > > + > > + /* Enabled via shmem mount options or sysfs settings. */ > > + if (shmem_file(vma->vm_file)) > > + return shmem_huge_enabled(vma); > > > > /* THP settings require madvise. */ > > if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) > > return false; > > > > - /* Read-only file mappings need to be aligned for THP to work. */ > > + /* Only regular file is valid */ > > if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && > > - !inode_is_open_for_write(vma->vm_file->f_inode) && > > (vm_flags & VM_EXEC)) { > > - return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, > > - HPAGE_PMD_NR); > > + struct inode *inode = vma->vm_file->f_inode; > > + > > + return !inode_is_open_for_write(inode) && > > + S_ISREG(inode->i_mode); > > } > > > > if (!vma->anon_vma || vma->vm_ops) > > -- > > 2.26.2 > > >
