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.

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: Stephen Rothwell <sfr@canb.auug.org.au>

diff --git a/fs/exec.c b/fs/exec.c
index eb2a99793018de323d8ac92dcda71a47619c9f76..816c7e347c9c105dc92fa40e9a34c99d34a87caa 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 ca54d36d203ae4c598b53d4bb9b2df75e2d00e92..79f4f8ae43ecd391f34c6a5ad40914e306ae1850 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))