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 DD0F32641CC; Tue, 8 Apr 2025 11:53:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744113210; cv=none; b=H316P2ooTrTBwbnNC8f4haoGHgBL1Y0907UzRlGyyvSN13PGaUq/ZFXg8+MTVa+Exyd80X/njWqr0ZW/AE7hFsrMBCsZw/6y1mbs/UUcU8hB1/Y7ueGeJUZOEWweewUVwifLu75E6juYI2yonhgBPDBRs1xFxSC5jJdlmeE9FPc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744113210; c=relaxed/simple; bh=4n7BdKQY6t4HfQ7B3KtIa64X49JFeRoc8/ogycHfTto=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GWAzRTaP8uaxHmmoBqOzJpv/ppU98x0lfgr6/5zO6uhRsEu+J36eayQJiNVKIt/aUoyvpKTvvBDQRiqO8DFY0RYEHFDsCoecEynaajm3LSgjYqPefRek3vbGZtDSmHfngFEpGX3tUSkJybxRKI9mQuMwF+0WPiLqMXjRooysBbA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=iEnyXy6S; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="iEnyXy6S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6F042C4CEE5; Tue, 8 Apr 2025 11:53:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744113209; bh=4n7BdKQY6t4HfQ7B3KtIa64X49JFeRoc8/ogycHfTto=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iEnyXy6SG/JOTvkilEgeXJ+m6Y5g/Cowlxa32KhOGiCzXmd/NTe6FvknI/mTaq0uZ Bog0zs+HobqLvS0Rq0a0uuk2QmaMQDqgL3wGJn6wbbmWdf2pVi5sCh2DzdIrWaKUxo wXwlPuysRVlUq8kzHTLS1RydKIvwUtJCRQnHgZVs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hou Tao , Alexei Starovoitov , Sasha Levin Subject: [PATCH 6.6 075/268] bpf: Use preempt_count() directly in bpf_send_signal_common() Date: Tue, 8 Apr 2025 12:48:06 +0200 Message-ID: <20250408104830.521554401@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250408104828.499967190@linuxfoundation.org> References: <20250408104828.499967190@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hou Tao [ Upstream commit b4a8b5bba712a711d8ca1f7d04646db63f9c88f5 ] bpf_send_signal_common() uses preemptible() to check whether or not the current context is preemptible. If it is preemptible, it will use irq_work to send the signal asynchronously instead of trying to hold a spin-lock, because spin-lock is sleepable under PREEMPT_RT. However, preemptible() depends on CONFIG_PREEMPT_COUNT. When CONFIG_PREEMPT_COUNT is turned off (e.g., CONFIG_PREEMPT_VOLUNTARY=y), !preemptible() will be evaluated as 1 and bpf_send_signal_common() will use irq_work unconditionally. Fix it by unfolding "!preemptible()" and using "preempt_count() != 0 || irqs_disabled()" instead. Fixes: 87c544108b61 ("bpf: Send signals asynchronously if !preemptible") Signed-off-by: Hou Tao Link: https://lore.kernel.org/r/20250220042259.1583319-1-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- kernel/trace/bpf_trace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 9d8f60e0cb554..545393601be8c 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -853,7 +853,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type) if (unlikely(is_global_init(current))) return -EPERM; - if (!preemptible()) { + if (preempt_count() != 0 || irqs_disabled()) { /* Do an early check on signal validity. Otherwise, * the error is lost in deferred irq_work. */ -- 2.39.5