LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
* [PATCH] Add mmap_assert_locked() annotations to find_vma*()
@ 2021-07-31 17:53 Luigi Rizzo
  2021-08-01 19:33 ` Andrew Morton
  2021-08-03 16:08 ` Jason Gunthorpe
  0 siblings, 2 replies; 14+ messages in thread
From: Luigi Rizzo @ 2021-07-31 17:53 UTC (permalink / raw)
  To: linux-kernel, Andrew Morton, David Rientjes; +Cc: linux-mm, Luigi Rizzo

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@google.com>
---
 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


^ permalink raw reply	[flat|nested] 14+ messages in thread

end of thread, other threads:[~2021-08-04 21:22 UTC | newest]

Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-31 17:53 [PATCH] Add mmap_assert_locked() annotations to find_vma*() Luigi Rizzo
2021-08-01 19:33 ` Andrew Morton
2021-08-02  0:16   ` Luigi Rizzo
2021-08-02 21:11     ` Andrew Morton
2021-08-03 16:08 ` Jason Gunthorpe
2021-08-03 21:48   ` Luigi Rizzo
2021-08-03 23:07     ` Liam Howlett
2021-08-03 23:35       ` Jason Gunthorpe
2021-08-03 23:57         ` Luigi Rizzo
2021-08-04  5:12           ` Liam Howlett
2021-08-04 14:42       ` Jann Horn
2021-08-04 15:21         ` Jason Gunthorpe
2021-08-04 21:22           ` Jann Horn
2021-08-04 17:32         ` Liam Howlett

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox