From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A570863BB for ; Mon, 20 Feb 2023 13:59:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2B062C43442; Mon, 20 Feb 2023 13:59:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1676901582; bh=CnNDBsju5D2uzWzFIKuWM8hecqUDq8p+RDPq//03iQc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1pIyobQNw5KyGi36o+jrq0UpnqFHRkpp3fVNU7633FpVZ+Ig2tWkQwm5yZASDPc+b tV+9UYk4DShAUjCTvzgS3mSdn8uIKXe9WPWHTdRwb6cIwv4XPrgxGywCJ0hqOxIIhk FBOfdCNuOgw8YWDB+HGapjqC36IfyghHpHvqWNQQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+6cd18e123583550cf469@syzkaller.appspotmail.com, Tetsuo Handa , "Peter Zijlstra (Intel)" Subject: [PATCH 6.1 073/118] freezer,umh: Fix call_usermode_helper_exec() vs SIGKILL Date: Mon, 20 Feb 2023 14:36:29 +0100 Message-Id: <20230220133603.349883651@linuxfoundation.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230220133600.368809650@linuxfoundation.org> References: <20230220133600.368809650@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Peter Zijlstra commit eedeb787ebb53de5c5dcf7b7b39d01bf1b0f037d upstream. Tetsuo-San noted that commit f5d39b020809 ("freezer,sched: Rewrite core freezer logic") broke call_usermodehelper_exec() for the KILLABLE case. Specifically it was missed that the second, unconditional, wait_for_completion() was not optional and ensures the on-stack completion is unused before going out-of-scope. Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic") Reported-by: syzbot+6cd18e123583550cf469@syzkaller.appspotmail.com Reported-by: Tetsuo Handa Debugged-by: Tetsuo Handa Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/Y90ar35uKQoUrLEK@hirez.programming.kicks-ass.net Signed-off-by: Greg Kroah-Hartman --- kernel/umh.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/kernel/umh.c b/kernel/umh.c index 850631518665..fbf872c624cb 100644 --- a/kernel/umh.c +++ b/kernel/umh.c @@ -438,21 +438,27 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait) if (wait == UMH_NO_WAIT) /* task has freed sub_info */ goto unlock; - if (wait & UMH_KILLABLE) - state |= TASK_KILLABLE; - if (wait & UMH_FREEZABLE) state |= TASK_FREEZABLE; - retval = wait_for_completion_state(&done, state); - if (!retval) - goto wait_done; - if (wait & UMH_KILLABLE) { + retval = wait_for_completion_state(&done, state | TASK_KILLABLE); + if (!retval) + goto wait_done; + /* umh_complete() will see NULL and free sub_info */ if (xchg(&sub_info->complete, NULL)) goto unlock; + + /* + * fallthrough; in case of -ERESTARTSYS now do uninterruptible + * wait_for_completion_state(). Since umh_complete() shall call + * complete() in a moment if xchg() above returned NULL, this + * uninterruptible wait_for_completion_state() will not block + * SIGKILL'ed processes for long. + */ } + wait_for_completion_state(&done, state); wait_done: retval = sub_info->retval; -- 2.39.1