linux-kernel - [PATCH] exec: Copy oldsighand->action under spin-lock

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Date:   Mon, 7 Jun 2021 15:54:27 +0200
From:   Bernd Edlinger <bernd.edlinger@...mail.de>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Kees Cook <keescook@...omium.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] exec: Copy oldsighand->action under spin-lock

unshare_sighand should only access oldsighand->action
while holding oldsighand->siglock, to make sure that
newsighand->action is in a consistent state.

Signed-off-by: Bernd Edlinger <bernd.edlinger@...mail.de>
---
 fs/exec.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index d8af85f..8344fba 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1193,11 +1193,11 @@ static int unshare_sighand(struct task_struct *me)
 			return -ENOMEM;
 
 		refcount_set(&newsighand->count, 1);
-		memcpy(newsighand->action, oldsighand->action,
-		       sizeof(newsighand->action));
 
 		write_lock_irq(&tasklist_lock);
 		spin_lock(&oldsighand->siglock);
+		memcpy(newsighand->action, oldsighand->action,
+		       sizeof(newsighand->action));
 		rcu_assign_pointer(me->sighand, newsighand);
 		spin_unlock(&oldsighand->siglock);
 		write_unlock_irq(&tasklist_lock);
-- 
1.9.1