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.
Signed-off-by: Luigi Rizzo <lrizzo@xxxxxxxxxx>
---
fs/exec.c | 2 ++
mm/mmap.c | 2 ++
2 files changed, 4 insertions(+)
diff --git a/fs/exec.c b/fs/exec.c
index 38f63451b928..ac7603e985b4 100644
--- 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 ca54d36d203a..79f4f8ae43ec 100644
--- 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))
--
2.32.0.554.ge1b32706d8-goog
