lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 23 Sep 2021 15:28:56 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Petr Mladek <pmladek@...e.com> Cc: gor@...ux.ibm.com, jpoimboe@...hat.com, jikos@...nel.org, mbenes@...e.cz, mingo@...nel.org, linux-kernel@...r.kernel.org, joe.lawrence@...hat.com, fweisbec@...il.com, tglx@...utronix.de, hca@...ux.ibm.com, svens@...ux.ibm.com, sumanthk@...ux.ibm.com, live-patching@...r.kernel.org, paulmck@...nel.org Subject: Re: [RFC][PATCH 7/7] livepatch,context_tracking: Avoid disturbing NOHZ_FULL tasks On Thu, Sep 23, 2021 at 03:14:48PM +0200, Petr Mladek wrote: > IMHO, this is not safe: > > CPU0 CPU1 > > klp_check_task(A) > if (context_tracking_state_cpu(task_cpu(task)) == CONTEXT_USER) > goto complete; > > clear_tsk_thread_flag(task, TIF_PATCH_PENDING); > > # task switching to kernel space > klp_update_patch_state(A) > if (test_and_clear_tsk_thread_flag(task, TIF_PATCH_PENDING)) > //false > > # calling kernel code with old task->patch_state > > task->patch_state = klp_target_state; > > BANG: CPU0 sets task->patch_state when task A is already running > kernel code on CPU1. Why is that a problem? That is, who actually cares about task->patch_state ? I was under the impression that state was purely for klp itself, to track which task has observed the new state.
Powered by blists - more mailing lists