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_lock() 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@i-love.sakura.ne.jp: TOMOYO needs the same protection which get_arg_page() needs]
Link: https://lkml.kernel.org/r/58bb6bf7-a57e-8a40-e74b-39584b415152@i-love.sakura.ne.jp
Link: https://lkml.kernel.org/r/20210731175341.3458608-1-lrizzo@google.com
Signed-off-by: Luigi Rizzo <lrizzo@google.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/exec.c b/fs/exec.c
index 41a888d..fd292e9 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -217,8 +217,10 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
         * 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;
 

diff --git a/mm/mmap.c b/mm/mmap.c
index ca54d36..79f4f8a 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -534,6 +534,7 @@ static int find_vma_links(struct mm_struct *mm, unsigned long addr,
 {
        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 mm_struct *mm, unsigned long addr)
        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))

diff --git a/security/tomoyo/domain.c b/security/tomoyo/domain.c
index 98d9858..31af29f 100644 (file)
--- a/security/tomoyo/domain.c
+++ b/security/tomoyo/domain.c
@@ -897,6 +897,9 @@ bool tomoyo_dump_page(struct linux_binprm *bprm, unsigned long pos,
                      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_binprm *bprm, unsigned long pos,
        /*
         * 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];