From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4DDEC64EC4 for ; Fri, 10 Mar 2023 14:38:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232662AbjCJOiN (ORCPT ); Fri, 10 Mar 2023 09:38:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232699AbjCJOiH (ORCPT ); Fri, 10 Mar 2023 09:38:07 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 10D8D1204A2 for ; Fri, 10 Mar 2023 06:37:40 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 30872618B8 for ; Fri, 10 Mar 2023 14:37:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2583FC4339B; Fri, 10 Mar 2023 14:37:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1678459028; bh=+l7zOQ56DtVh0IMdm20/OB3CezTKlI53c4+VSHTH7Io=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fJUDts214uuxdSPhN1s+hQ/JWt4MMqYSQNpv9Tf3Fed4+uDQ3Td/t9CllFGZRKhBJ VtCClQbkSM9G0hT6NjQf8Aj5jqKMNg5ocmXDdfjZv+6MhzVt9Bc93TGbBt67rPn2yQ nAOttS16na6+YnfRTSm+2wszPiYCdRya3fdw9NbQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Heiko Carstens , Vasily Gorbik Subject: [PATCH 5.4 217/357] s390/kprobes: fix current_kprobe never cleared after kprobes reenter Date: Fri, 10 Mar 2023 14:38:26 +0100 Message-Id: <20230310133744.284882174@linuxfoundation.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230310133733.973883071@linuxfoundation.org> References: <20230310133733.973883071@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Vasily Gorbik commit cd57953936f2213dfaccce10d20f396956222c7d upstream. Recent test_kprobe_missed kprobes kunit test uncovers the following problem. Once kprobe is triggered from another kprobe (kprobe reenter), all future kprobes on this cpu are considered as kprobe reenter, thus pre_handler and post_handler are not being called and kprobes are counted as "missed". Commit b9599798f953 ("[S390] kprobes: activation and deactivation") introduced a simpler scheme for kprobes (de)activation and status tracking by using push_kprobe/pop_kprobe, which supposed to work for both initial kprobe entry as well as kprobe reentry and helps to avoid handling those two cases differently. The problem is that a sequence of calls in case of kprobes reenter: push_kprobe() <- NULL (current_kprobe) push_kprobe() <- kprobe1 (current_kprobe) pop_kprobe() -> kprobe1 (current_kprobe) pop_kprobe() -> kprobe1 (current_kprobe) leaves "kprobe1" as "current_kprobe" on this cpu, instead of setting it to NULL. In fact push_kprobe/pop_kprobe can only store a single state (there is just one prev_kprobe in kprobe_ctlblk). Which is a hack but sufficient, there is no need to have another prev_kprobe just to store NULL. To make a simple and backportable fix simply reset "prev_kprobe" when kprobe is poped from this "stack". No need to worry about "kprobe_status" in this case, because its value is only checked when current_kprobe != NULL. Cc: stable@vger.kernel.org Fixes: b9599798f953 ("[S390] kprobes: activation and deactivation") Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Heiko Carstens Signed-off-by: Greg Kroah-Hartman --- arch/s390/kernel/kprobes.c | 1 + 1 file changed, 1 insertion(+) --- a/arch/s390/kernel/kprobes.c +++ b/arch/s390/kernel/kprobes.c @@ -255,6 +255,7 @@ static void pop_kprobe(struct kprobe_ctl { __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); kcb->kprobe_status = kcb->prev_kprobe.status; + kcb->prev_kprobe.kp = NULL; } NOKPROBE_SYMBOL(pop_kprobe);