From: Luigi Rizzo <lrizzo@xxxxxxxxxx> Subject: mm/pagemap: add mmap_assert_locked() annotations to find_vma*() find_vma() and variants need protection when used. This patch adds mmap_assert_lock() calls in the functions. To make sure the invariant is satisfied, we also need to add a mmap_read_loc() around the get_user_pages_remote() call in get_arg_page(). The lock is not strictly necessary because the mm has been newly created, but the extra cost is limited because the same mutex was also acquired shortly before in __bprm_mm_init(), so it is hot and uncontended. [penguin-kernel@xxxxxxxxxxxxxxxxxxx: TOMOYO needs the same protection which get_arg_page() needs] Link: https://lkml.kernel.org/r/58bb6bf7-a57e-8a40-e74b-39584b415152@xxxxxxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20210731175341.3458608-1-lrizzo@xxxxxxxxxx Signed-off-by: Luigi Rizzo <lrizzo@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/exec.c | 2 ++ mm/mmap.c | 2 ++ security/tomoyo/domain.c | 13 +++++++++---- 3 files changed, 13 insertions(+), 4 deletions(-) --- a/fs/exec.c~add-mmap_assert_locked-annotations-to-find_vma +++ a/fs/exec.c @@ -217,8 +217,10 @@ static struct page *get_arg_page(struct * We are doing an exec(). 'current' is the process * doing the exec and bprm->mm is the new process's mm. */ + mmap_read_lock(bprm->mm); ret = get_user_pages_remote(bprm->mm, pos, 1, gup_flags, &page, NULL, NULL); + mmap_read_unlock(bprm->mm); if (ret <= 0) return NULL; --- a/mm/mmap.c~add-mmap_assert_locked-annotations-to-find_vma +++ a/mm/mmap.c @@ -534,6 +534,7 @@ static int find_vma_links(struct mm_stru { struct rb_node **__rb_link, *__rb_parent, *rb_prev; + mmap_assert_locked(mm); __rb_link = &mm->mm_rb.rb_node; rb_prev = __rb_parent = NULL; @@ -2303,6 +2304,7 @@ struct vm_area_struct *find_vma(struct m struct rb_node *rb_node; struct vm_area_struct *vma; + mmap_assert_locked(mm); /* Check the cache first. */ vma = vmacache_find(mm, addr); if (likely(vma)) --- a/security/tomoyo/domain.c~add-mmap_assert_locked-annotations-to-find_vma +++ a/security/tomoyo/domain.c @@ -897,6 +897,9 @@ bool tomoyo_dump_page(struct linux_binpr struct tomoyo_page_dump *dump) { struct page *page; +#ifdef CONFIG_MMU + int ret; +#endif /* dump->data is released by tomoyo_find_next_domain(). */ if (!dump->data) { @@ -909,11 +912,13 @@ bool tomoyo_dump_page(struct linux_binpr /* * This is called at execve() time in order to dig around * in the argv/environment of the new proceess - * (represented by bprm). 'current' is the process doing - * the execve(). + * (represented by bprm). */ - if (get_user_pages_remote(bprm->mm, pos, 1, - FOLL_FORCE, &page, NULL, NULL) <= 0) + mmap_read_lock(bprm->mm); + ret = get_user_pages_remote(bprm->mm, pos, 1, + FOLL_FORCE, &page, NULL, NULL); + mmap_read_unlock(bprm->mm); + if (ret <= 0) return false; #else page = bprm->page[pos / PAGE_SIZE]; _
