From patchwork Wed May 17 03:45:07 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ze Gao X-Patchwork-Id: 13244144 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 6A4FC2100 for ; Wed, 17 May 2023 03:45:34 +0000 (UTC) Received: from mail-pl1-x62e.google.com (mail-pl1-x62e.google.com [IPv6:2607:f8b0:4864:20::62e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CB4EA46AE; Tue, 16 May 2023 20:45:32 -0700 (PDT) Received: by mail-pl1-x62e.google.com with SMTP id d9443c01a7336-1ae3ed1b08eso4283735ad.0; Tue, 16 May 2023 20:45:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1684295132; x=1686887132; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=qGFBel0XWHMPBOQVpTEFEgbDNqzL0utWuk4Q5TTOH0I=; b=mnJfkgKpTPVHwlmswT6XPsXRmkE2FWCwvioj+muJ+uq/kD9S+KoY7Oqkt6AmGwLc/z XybyjbtWhNsEukNAJTd2qEGYk9Q5aG8qQhF8Z4c8fxEuhIHJSB7pGjzeyBHZ7eLCJ0ws Hu70LM7ImU/s5A9/ULM7FjA2T3Cgn6aORaqGmDC7TbFFn0Bjdn8aMd7V1ebFyyUDDS+/ ijzbOIGTn234aKxai/0GSHN1oxWvmXwJgoQ3LE8py0PO78r1+r5FrFv/U8FACfsqgf2s 1dsyFbjtjgmr6jCqTC1Vroc6QGGr3250tlPm4Rp5GQjBasJ1Y6NSlI+mvnKXJhm6Sq/g MJ0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684295132; x=1686887132; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qGFBel0XWHMPBOQVpTEFEgbDNqzL0utWuk4Q5TTOH0I=; b=i/7IHYjqFFrgqfnXsIpp8niZUr9k0YacnK+jL/ifglWQRtJ5hYNGKPlNj/pchbf7kG GLFNF71CO+mwzeSnKayBqJEKIs7q/id4s9IpjHQCeop+lqqEMwrkzFD3TXwey8nqKPhT zN95yPmFa1mM1qXrDylaF7sX3JBBo4MPH4FXVSJBEKfHfUzLdBqZ8oc2BY3dWqAPNWf3 XngveA4HvSp6YqToaoD1vLbAcAxuSejr6DOuB9pkj+h0rnskDlqWHv96b7hWVU5PA3ag yNzO9S5TTJ/tOoi0ig9EMJqmzzR+D2SXJSwkLQFXuNUHVRW9ZCcr4gWs2EsAAMtM6uph SX6g== X-Gm-Message-State: AC+VfDxVg2Jyt6KfTI9mSUP+x4ZffeLEPT2TPzjq+yDeW49LLTmTK84F 5+YoqYnDHV5UnUp00hJnlgI= X-Google-Smtp-Source: ACHHUZ5LPHotl0fJ/O3KGBLfATUmV2Ofpz6WW1a3qNWCMnkfgz1soa2zRJ+uMCkiFPlag6APwqkb4A== X-Received: by 2002:a17:902:d507:b0:1ac:310d:872d with SMTP id b7-20020a170902d50700b001ac310d872dmr52041365plg.52.1684295132086; Tue, 16 May 2023 20:45:32 -0700 (PDT) Received: from localhost.localdomain ([203.205.141.83]) by smtp.googlemail.com with ESMTPSA id t2-20020a170902e84200b001a19196af48sm16336746plg.64.2023.05.16.20.45.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 May 2023 20:45:31 -0700 (PDT) From: Ze Gao X-Google-Original-From: Ze Gao To: Steven Rostedt , Masami Hiramatsu Cc: Albert Ou , Alexander Gordeev , Alexei Starovoitov , Borislav Petkov , Christian Borntraeger , Dave Hansen , Heiko Carstens , "H. Peter Anvin" , Ingo Molnar , Palmer Dabbelt , Paul Walmsley , Sven Schnelle , Thomas Gleixner , Vasily Gorbik , x86@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Conor Dooley , Jiri Olsa , Yonghong Song , Ze Gao Subject: [PATCH v3 2/4] fprobe: make fprobe_kprobe_handler recursion free Date: Wed, 17 May 2023 11:45:07 +0800 Message-Id: <20230517034510.15639-3-zegao@tencent.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230517034510.15639-1-zegao@tencent.com> References: <20230517034510.15639-1-zegao@tencent.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Current implementation calls kprobe related functions before doing ftrace recursion check in fprobe_kprobe_handler, which opens door to kernel crash due to stack recursion if preempt_count_{add, sub} is traceable in kprobe_busy_{begin, end}. Things goes like this without this patch quoted from Steven: " fprobe_kprobe_handler() { kprobe_busy_begin() { preempt_disable() { preempt_count_add() { <-- trace fprobe_kprobe_handler() { [ wash, rinse, repeat, CRASH!!! ] " By refactoring the common part out of fprobe_kprobe_handler and fprobe_handler and call ftrace recursion detection at the very beginning, the whole fprobe_kprobe_handler is free from recursion. Signed-off-by: Ze Gao Acked-by: Masami Hiramatsu (Google) Link: https://lore.kernel.org/linux-trace-kernel/20230516071830.8190-3-zegao@tencent.com --- kernel/trace/fprobe.c | 59 ++++++++++++++++++++++++++++++++----------- 1 file changed, 44 insertions(+), 15 deletions(-) diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 9abb3905bc8e..097c740799ba 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -20,30 +20,22 @@ struct fprobe_rethook_node { char data[]; }; -static void fprobe_handler(unsigned long ip, unsigned long parent_ip, - struct ftrace_ops *ops, struct ftrace_regs *fregs) +static inline void __fprobe_handler(unsigned long ip, unsigned long + parent_ip, struct ftrace_ops *ops, struct ftrace_regs *fregs) { struct fprobe_rethook_node *fpr; struct rethook_node *rh = NULL; struct fprobe *fp; void *entry_data = NULL; - int bit, ret; + int ret; fp = container_of(ops, struct fprobe, ops); - if (fprobe_disabled(fp)) - return; - - bit = ftrace_test_recursion_trylock(ip, parent_ip); - if (bit < 0) { - fp->nmissed++; - return; - } if (fp->exit_handler) { rh = rethook_try_get(fp->rethook); if (!rh) { fp->nmissed++; - goto out; + return; } fpr = container_of(rh, struct fprobe_rethook_node, node); fpr->entry_ip = ip; @@ -61,23 +53,60 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip, else rethook_hook(rh, ftrace_get_regs(fregs), true); } -out: +} + +static void fprobe_handler(unsigned long ip, unsigned long parent_ip, + struct ftrace_ops *ops, struct ftrace_regs *fregs) +{ + struct fprobe *fp; + int bit; + + fp = container_of(ops, struct fprobe, ops); + if (fprobe_disabled(fp)) + return; + + /* recursion detection has to go before any traceable function and + * all functions before this point should be marked as notrace + */ + bit = ftrace_test_recursion_trylock(ip, parent_ip); + if (bit < 0) { + fp->nmissed++; + return; + } + __fprobe_handler(ip, parent_ip, ops, fregs); ftrace_test_recursion_unlock(bit); + } NOKPROBE_SYMBOL(fprobe_handler); static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *ops, struct ftrace_regs *fregs) { - struct fprobe *fp = container_of(ops, struct fprobe, ops); + struct fprobe *fp; + int bit; + + fp = container_of(ops, struct fprobe, ops); + if (fprobe_disabled(fp)) + return; + + /* recursion detection has to go before any traceable function and + * all functions called before this point should be marked as notrace + */ + bit = ftrace_test_recursion_trylock(ip, parent_ip); + if (bit < 0) { + fp->nmissed++; + return; + } if (unlikely(kprobe_running())) { fp->nmissed++; return; } + kprobe_busy_begin(); - fprobe_handler(ip, parent_ip, ops, fregs); + __fprobe_handler(ip, parent_ip, ops, fregs); kprobe_busy_end(); + ftrace_test_recursion_unlock(bit); } static void fprobe_exit_handler(struct rethook_node *rh, void *data,