From patchwork Fri Oct 9 12:58:34 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrey Konovalov X-Patchwork-Id: 11825795 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B1A1A109B for ; Fri, 9 Oct 2020 12:58:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 85D9A222C4 for ; Fri, 9 Oct 2020 12:58:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="AcdN/R8j" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387894AbgJIM6o (ORCPT ); Fri, 9 Oct 2020 08:58:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39368 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732521AbgJIM6o (ORCPT ); Fri, 9 Oct 2020 08:58:44 -0400 Received: from mail-wr1-x449.google.com (mail-wr1-x449.google.com [IPv6:2a00:1450:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C6D3C0613D2 for ; Fri, 9 Oct 2020 05:58:44 -0700 (PDT) Received: by mail-wr1-x449.google.com with SMTP id g7so5250194wrm.2 for ; Fri, 09 Oct 2020 05:58:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:message-id:mime-version:subject:from:to:cc; bh=1SLpeoVP+KmJ3MNjUMrmmSJBrm2VlkC1VfYu1S5MKOc=; b=AcdN/R8jskNNTOM90JrNrRpkSI8CeziorVJ+MAqF9JiYxByIkTxHESGQUi0ElNaFkE HjxPX01gGLdzSYrZhlrkFwImvWHyoZ5SAuWC3Okc3QfgQh3sKwItSaqOJzCdAWZ2OKyx fGs1zlcjKx31e5QJrau6qHMlSjMTqQ0Z2JjoiL5CHOz2j3xBgL8XrELvHsx/tHJfVwxR PP+9p7Sfq2Y18IWS+ZjwpKRp6ctqtXI19G4nExjAQD1U+YEG2w7+D3Us48AYrwrcgdyA nax4BEeJnRj/qEeuJsXtCPOHmY5qW0T9ryNkhZuJM6W7wqbZPIhqA+JXFtHuw2JXFxuG u22w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:message-id:mime-version:subject:from :to:cc; bh=1SLpeoVP+KmJ3MNjUMrmmSJBrm2VlkC1VfYu1S5MKOc=; b=bTOGiI1sxGf9TBDTlzUA/19dtS5mhgoUu/N6DYO32AkF2fm4quz9oc4araC0T5SW6h G1d1p7bVZvqTftvFnr1wH1eudnDyktW7CZ5UjQiHOM1XWeQhEZhAHfdhW/KAfClASsmK i3VaXYNUn6Np+FwXGyAPoPCUyYgyUJ0pPWIewi4gbp9HPY8D17JMEYRO/SPJ/nr4kLGH VQNNdk+ZUWDrX1XpyNZegCqO9gK+MuPUDPpLMAf3n1xoWA2nhOUwrrhNiIEj82UaNrgx dKv6XY0gcrU0wMZpBnHh41IZsHYOXAIdJhThbfwCMJlz/yXuKuTGrl6NM8cjHpODsBjJ fA1g== X-Gm-Message-State: AOAM532z+fsqa5UlCnQDE9DqgfE2ElhHTdkKj/AHmyaawr4ZAUdfhIVS pgCnUPZNeM2uG5mtTZl85IGRFDJ84iNFReMg X-Google-Smtp-Source: ABdhPJxwPJ9TgDYr/md/gHUwGfwT0fxi/fRK9KN0oN6wSg18o9sJ4tk6dGvjYtjfYWgLB8clRmd1RVVlHe95vWo7 Sender: "andreyknvl via sendgmr" X-Received: from andreyknvl3.muc.corp.google.com ([2a00:79e0:15:13:7220:84ff:fe09:7e9d]) (user=andreyknvl job=sendgmr) by 2002:a7b:c345:: with SMTP id l5mr13883075wmj.123.1602248322770; Fri, 09 Oct 2020 05:58:42 -0700 (PDT) Date: Fri, 9 Oct 2020 14:58:34 +0200 Message-Id: <223901affc7bd759b2d6995c2dbfbdd0a29bc88a.1602248029.git.andreyknvl@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.28.0.1011.ga647a8990f-goog Subject: [PATCH v2] kcov, usb, vhost: specify contexts for remote coverage sections From: Andrey Konovalov To: Dmitry Vyukov Cc: Andrew Morton , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Alan Stern , Shuah Khan , Alexander Potapenko , Marco Elver , Aleksandr Nogikh , Nazime Hande Harputluoglu , Andrey Konovalov Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Currently there's a KCOV remote coverage collection section in __usb_hcd_giveback_urb(). Initially that section was added based on the assumption that usb_hcd_giveback_urb() can only be called in interrupt context as indicated by a comment before it. This is what happens when syzkaller is fuzzing the USB stack via the dummy_hcd driver. As it turns out, it's actually valid to call usb_hcd_giveback_urb() in task context, provided that the caller turned off the interrupts; USB/IP does exactly that. This can lead to a nested KCOV remote coverage collection sections both trying to collect coverage in task context. This isn't supported by KCOV, and leads to a WARNING. The approach this patch takes is to annotate every call of kcov_remote_*() callbacks with the context those callbacks are supposed to be executed in. If the current context doesn't match the mask provided to a callback, that callback is ignored. KCOV currently only supports collecting remote coverage in two contexts: task and softirq. This patch constraints KCOV to only collect coverage from __usb_hcd_giveback_urb() when it's executed in softirq context. As the result, the coverage from USB/IP related usb_hcd_giveback_urb() calls won't be collected, but the WARNING is fixed. A potential future improvement would be to support nested remote coverage collection sections, but this patch doesn't address that. Signed-off-by: Andrey Konovalov Reported-by: kernel test robot Reported-by: kernel test robot --- Changes v1->v2: - Fix context checks in kcov_remote_start/stop(). - Clarify commit description. --- Documentation/dev-tools/kcov.rst | 5 +++++ drivers/usb/core/hcd.c | 4 ++-- drivers/usb/core/hub.c | 4 ++-- drivers/vhost/vhost.c | 5 +++-- include/linux/kcov.h | 24 ++++++++++++++---------- kernel/kcov.c | 16 ++++++++++++---- 6 files changed, 38 insertions(+), 20 deletions(-) diff --git a/Documentation/dev-tools/kcov.rst b/Documentation/dev-tools/kcov.rst index 8548b0b04e43..99fda94a34c5 100644 --- a/Documentation/dev-tools/kcov.rst +++ b/Documentation/dev-tools/kcov.rst @@ -235,6 +235,11 @@ saved to the kcov_handle field in the current task_struct and needs to be passed to the newly spawned threads via custom annotations. Those threads should in turn be annotated with kcov_remote_start()/kcov_remote_stop(). +Besides a handle, kcov_remote_start()/kcov_remote_stop() annotations accept +a context mask. This mask describes the contexts in which these annotations +should be applied. E.g. specifying KCOV_CONTEXT_SOFTIRQ will result in the +corresponding annotations being ignored in any context other than softirq. + Internally kcov stores handles as u64 integers. The top byte of a handle is used to denote the id of a subsystem that this handle belongs to, and the lower 4 bytes are used to denote the id of a thread instance within diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c index a33b849e8beb..1b090e3218a8 100644 --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -1646,9 +1646,9 @@ static void __usb_hcd_giveback_urb(struct urb *urb) /* pass ownership to the completion handler */ urb->status = status; - kcov_remote_start_usb((u64)urb->dev->bus->busnum); + kcov_remote_start_usb((u64)urb->dev->bus->busnum, KCOV_CONTEXT_SOFTIRQ); urb->complete(urb); - kcov_remote_stop(); + kcov_remote_stop(KCOV_CONTEXT_SOFTIRQ); usb_anchor_resume_wakeups(anchor); atomic_dec(&urb->use_count); diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 5b768b80d1ee..d17db72dd020 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -5509,7 +5509,7 @@ static void hub_event(struct work_struct *work) hub_dev = hub->intfdev; intf = to_usb_interface(hub_dev); - kcov_remote_start_usb((u64)hdev->bus->busnum); + kcov_remote_start_usb((u64)hdev->bus->busnum, KCOV_CONTEXT_TASK); dev_dbg(hub_dev, "state %d ports %d chg %04x evt %04x\n", hdev->state, hdev->maxchild, @@ -5618,7 +5618,7 @@ static void hub_event(struct work_struct *work) usb_autopm_put_interface(intf); kref_put(&hub->kref, hub_release); - kcov_remote_stop(); + kcov_remote_stop(KCOV_CONTEXT_TASK); } static const struct usb_device_id hub_id_table[] = { diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index b45519ca66a7..8913de414e89 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -363,9 +363,10 @@ static int vhost_worker(void *data) llist_for_each_entry_safe(work, work_next, node, node) { clear_bit(VHOST_WORK_QUEUED, &work->flags); __set_current_state(TASK_RUNNING); - kcov_remote_start_common(dev->kcov_handle); + kcov_remote_start_common(dev->kcov_handle, + KCOV_CONTEXT_TASK); work->fn(work); - kcov_remote_stop(); + kcov_remote_stop(KCOV_CONTEXT_TASK); if (need_resched()) schedule(); } diff --git a/include/linux/kcov.h b/include/linux/kcov.h index a10e84707d82..507003038918 100644 --- a/include/linux/kcov.h +++ b/include/linux/kcov.h @@ -22,6 +22,10 @@ enum kcov_mode { KCOV_MODE_TRACE_CMP = 3, }; +#define KCOV_CONTEXT_TASK (1u << 0) +#define KCOV_CONTEXT_SOFTIRQ (1u << 1) +#define KCOV_CONTEXT_MASK (KCOV_CONTEXT_TASK | KCOV_CONTEXT_SOFTIRQ) + #define KCOV_IN_CTXSW (1 << 30) void kcov_task_init(struct task_struct *t); @@ -38,18 +42,18 @@ do { \ } while (0) /* See Documentation/dev-tools/kcov.rst for usage details. */ -void kcov_remote_start(u64 handle); -void kcov_remote_stop(void); +void kcov_remote_start(u64 handle, unsigned int context); +void kcov_remote_stop(unsigned int context); u64 kcov_common_handle(void); -static inline void kcov_remote_start_common(u64 id) +static inline void kcov_remote_start_common(u64 id, unsigned int context) { - kcov_remote_start(kcov_remote_handle(KCOV_SUBSYSTEM_COMMON, id)); + kcov_remote_start(kcov_remote_handle(KCOV_SUBSYSTEM_COMMON, id), context); } -static inline void kcov_remote_start_usb(u64 id) +static inline void kcov_remote_start_usb(u64 id, unsigned int context) { - kcov_remote_start(kcov_remote_handle(KCOV_SUBSYSTEM_USB, id)); + kcov_remote_start(kcov_remote_handle(KCOV_SUBSYSTEM_USB, id), context); } #else @@ -58,14 +62,14 @@ static inline void kcov_task_init(struct task_struct *t) {} static inline void kcov_task_exit(struct task_struct *t) {} static inline void kcov_prepare_switch(struct task_struct *t) {} static inline void kcov_finish_switch(struct task_struct *t) {} -static inline void kcov_remote_start(u64 handle) {} -static inline void kcov_remote_stop(void) {} +static inline void kcov_remote_start(u64 handle, unsigned int context) {} +static inline void kcov_remote_stop(unsigned int context) {} static inline u64 kcov_common_handle(void) { return 0; } -static inline void kcov_remote_start_common(u64 id) {} -static inline void kcov_remote_start_usb(u64 id) {} +static inline void kcov_remote_start_common(u64 id, unsigned int context) {} +static inline void kcov_remote_start_usb(u64 id, unsigned int context) {} #endif /* CONFIG_KCOV */ #endif /* _LINUX_KCOV_H */ diff --git a/kernel/kcov.c b/kernel/kcov.c index 6b8368be89c8..e4475b63d6be 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -808,7 +808,7 @@ static void kcov_remote_softirq_stop(struct task_struct *t) } } -void kcov_remote_start(u64 handle) +void kcov_remote_start(u64 handle, unsigned int context) { struct task_struct *t = current; struct kcov_remote *remote; @@ -821,7 +821,11 @@ void kcov_remote_start(u64 handle) if (WARN_ON(!kcov_check_handle(handle, true, true, true))) return; - if (!in_task() && !in_serving_softirq()) + if (WARN_ON((context & ~KCOV_CONTEXT_MASK) || !context)) + return; + if (in_task() && !(context & KCOV_CONTEXT_TASK)) + return; + if (in_serving_softirq() && !(context & KCOV_CONTEXT_SOFTIRQ)) return; local_irq_save(flags); @@ -952,7 +956,7 @@ static void kcov_move_area(enum kcov_mode mode, void *dst_area, } /* See the comment before kcov_remote_start() for usage details. */ -void kcov_remote_stop(void) +void kcov_remote_stop(unsigned int context) { struct task_struct *t = current; struct kcov *kcov; @@ -962,7 +966,11 @@ void kcov_remote_stop(void) int sequence; unsigned long flags; - if (!in_task() && !in_serving_softirq()) + if (WARN_ON((context & ~KCOV_CONTEXT_MASK) || !context)) + return; + if (in_task() && !(context & KCOV_CONTEXT_TASK)) + return; + if (in_serving_softirq() && !(context & KCOV_CONTEXT_SOFTIRQ)) return; local_irq_save(flags);