57 lines
2.3 KiB
Diff
57 lines
2.3 KiB
Diff
From 2f3e5b5a77374869a5c36c783c310be9c26493e0 Mon Sep 17 00:00:00 2001
|
|
From: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>
|
|
Date: Thu, 28 May 2026 15:18:57 +0000
|
|
Subject: [PATCH] exit: prevent preemption of oopsing TASK_DEAD task
|
|
|
|
JIRA: https://redhat.atlassian.net/browse/RHEL-180008
|
|
CVE: CVE-2026-46173
|
|
Backported from tree(s): linux
|
|
|
|
commit c1fa0bb633e4a6b11e83ffc57fa5abe8ebb87891
|
|
Author: Jann Horn <jannh@google.com>
|
|
Date: Mon May 11 08:55:11 2026 -0700
|
|
|
|
exit: prevent preemption of oopsing TASK_DEAD task
|
|
|
|
When an already-exiting task oopses, make_task_dead() currently calls
|
|
do_task_dead() with preemption enabled. That is forbidden:
|
|
do_task_dead() calls __schedule(), which has a comment saying "WARNING:
|
|
must be called with preemption disabled!".
|
|
|
|
If an oopsing task is preempted in do_task_dead(), between becoming
|
|
TASK_DEAD and entering the scheduler explicitly, bad things happen:
|
|
finish_task_switch() assumes that once the scheduler has switched away
|
|
from a TASK_DEAD task, the task can never run again and its stack is no
|
|
longer needed; but that assumption apparently doesn't hold if the dead
|
|
task was preempted (the SM_PREEMPT case).
|
|
|
|
This means that the scheduler ends up repeatedly dropping references on
|
|
the dead task's stack, which can lead to use-after-free or double-free
|
|
of the entire task stack; in other words, two tasks can end up running
|
|
on the same stack, resulting in various kinds of memory corruption.
|
|
|
|
(This does not just affect "recursively oopsing" tasks; it is enough to
|
|
oops once during task exit, for example in a file_operations::release
|
|
handler)
|
|
|
|
Fixes: 7f80a2fd7db9 ("exit: Stop poorly open coding do_task_dead in make_task_dead")
|
|
Cc: stable@kernel.org
|
|
Signed-off-by: Jann Horn <jannh@google.com>
|
|
Acked-by: Peter Zijlstra <peterz@infradead.org>
|
|
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
|
|
Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>
|
|
|
|
diff --git a/kernel/exit.c b/kernel/exit.c
|
|
index aa08b46..6a1081a 100644
|
|
--- a/kernel/exit.c
|
|
+++ b/kernel/exit.c
|
|
@@ -959,6 +959,7 @@ void __noreturn make_task_dead(int signr)
|
|
futex_exit_recursive(tsk);
|
|
tsk->exit_state = EXIT_DEAD;
|
|
refcount_inc(&tsk->rcu_users);
|
|
+ preempt_disable();
|
|
do_task_dead();
|
|
}
|
|
|