linux-kernel - [PATCH 4/6] exec: Run sync_mm_rss before taking exec_update

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Message-ID: <875zd66za3.fsf_-_@x220.int.ebiederm.org>
Date:   Fri, 08 May 2020 13:45:56 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     <linux-kernel@...r.kernel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>, Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Rob Landley <rob@...dley.net>,
        Bernd Edlinger <bernd.edlinger@...mail.de>,
        <linux-fsdevel@...r.kernel.org>, Al Viro <viro@...IV.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 4/6] exec: Run sync_mm_rss before taking exec_update_mutex


Like exec_mm_release sync_mm_rss is about flushing out the state of
the old_mm, which does not need to happen under exec_update_mutex.

Make this explicit by moving sync_mm_rss outside of exec_update_mutex.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 fs/exec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/exec.c b/fs/exec.c
index 11a5c073aa35..15682a1dfee9 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1051,13 +1051,14 @@ static int exec_mmap(struct mm_struct *mm)
 	tsk = current;
 	old_mm = current->mm;
 	exec_mm_release(tsk, old_mm);
+	if (old_mm)
+		sync_mm_rss(old_mm);
 
 	ret = mutex_lock_killable(&tsk->signal->exec_update_mutex);
 	if (ret)
 		return ret;
 
 	if (old_mm) {
-		sync_mm_rss(old_mm);
 		/*
 		 * Make sure that if there is a core dump in progress
 		 * for the old mm, we get out and die instead of going
-- 
2.20.1