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
--- 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;