From nobody Fri Oct 3 14:29:31 2025 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (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 597FE30CD84 for ; Fri, 29 Aug 2025 02:14:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756433690; cv=none; b=LRpY9vpx96TXN9iL02h12TOVz/VbpCUVQS4CrEZHEN1l93m1tyzjB4EfaOcD2GLI0HK49QM8IZ39ku412FPvIUvpiJodstKluJ9qzx80Yvwk+ceSjqedCPfo9AxSAvymV4/ptDGknZKzvUbmmYqcxse7m9TDRpy6PPuKoHQ4WCI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756433690; c=relaxed/simple; bh=jHPXfkFeIwjt4mfYaOe/rVaJ3mviT+kE7KTC7JsGT6Y=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=kRJX7Sak7g3J8ss7ugvoYq7kaIXv8NRzZxq8ktlV8prN0gs3EKuZj3ZNQT9naOS1iB3Bo6d/Z9QhldyX8MjjOh2kfj4PWziX4mq7f6sW66RXxGBtDjvKh+r5zHy+GTPEi5hnL5zmCDcCalozaweOFteuIrXDeNfO37LyHn3QTRc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=chinatelecom.cn; spf=pass smtp.mailfrom=linux.dev; arc=none smtp.client-ip=91.218.175.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=chinatelecom.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Menglong Dong To: mhiramat@kernel.org Cc: rostedt@goodmis.org, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, kernel test robot Subject: [PATCH] tracing: fprobe: fix suspicious rcu usage in fprobe_entry Date: Fri, 29 Aug 2025 10:14:36 +0800 Message-ID: <20250829021436.19982-1-dongml2@chinatelecom.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" rcu_read_lock() is not needed in fprobe_entry, but rcu_dereference_check() is used in rhltable_lookup(), which causes suspicious RCU usage warning: WARNING: suspicious RCU usage 6.17.0-rc1-00001-gdfe0d675df82 #1 Tainted: G S ----------------------------- include/linux/rhashtable.h:602 suspicious rcu_dereference_check() usage! ...... stack backtrace: CPU: 1 UID: 0 PID: 4652 Comm: ftracetest Tainted: G S Tainted: [S]=3DCPU_OUT_OF_SPEC, [I]=3DFIRMWARE_WORKAROUND Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.1.1 10/07/2015 Call Trace: dump_stack_lvl+0x7c/0x90 lockdep_rcu_suspicious+0x14f/0x1c0 __rhashtable_lookup+0x1e0/0x260 ? __pfx_kernel_clone+0x10/0x10 fprobe_entry+0x9a/0x450 ? __lock_acquire+0x6b0/0xca0 ? find_held_lock+0x2b/0x80 ? __pfx_fprobe_entry+0x10/0x10 ? __pfx_kernel_clone+0x10/0x10 ? lock_acquire+0x14c/0x2d0 ? __might_fault+0x74/0xc0 function_graph_enter_regs+0x2a0/0x550 ? __do_sys_clone+0xb5/0x100 ? __pfx_function_graph_enter_regs+0x10/0x10 ? _copy_to_user+0x58/0x70 ? __pfx_kernel_clone+0x10/0x10 ? __x64_sys_rt_sigprocmask+0x114/0x180 ? __pfx___x64_sys_rt_sigprocmask+0x10/0x10 ? __pfx_kernel_clone+0x10/0x10 ftrace_graph_func+0x87/0xb0 Fix this by using rcu_read_lock() for rhltable_lookup(). Alternatively, we can use rcu_lock_acquire(&rcu_lock_map) here to obtain better performance. However, it's not a common usage :/ Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202508281655.54c87330-lkp@intel.com Fixes: dfe0d675df82 ("tracing: fprobe: use rhltable for fprobe_ip_table") Signed-off-by: Menglong Dong --- kernel/trace/fprobe.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index fb127fa95f21..fece0f849c1c 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -269,7 +269,9 @@ static int fprobe_entry(struct ftrace_graph_ent *trace,= struct fgraph_ops *gops, if (WARN_ON_ONCE(!fregs)) return 0; =20 + rcu_read_lock(); head =3D rhltable_lookup(&fprobe_ip_table, &func, fprobe_rht_params); + rcu_read_unlock(); reserved_words =3D 0; rhl_for_each_entry_rcu(node, pos, head, hlist) { if (node->addr !=3D func) --=20 2.51.0