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 A4A2120A5C3; Tue, 8 Apr 2025 12:46:39 +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=1744116399; cv=none; b=iYIoAESK5SHL1InV8c23jUgE5YkaXl3b1MEZMBNcbI1EU+HpWIkfEtbKJpGUaD9AhvAw9iRcxovSIJ1jWMtS5eE71+Vw6RYh6WGZSZcVtNyDS86SQBrQ4m2EZfDe6blu0KeAcH5uPVnMFczNIboh1O+STV+HjRAAsNCu+rBdpmM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744116399; c=relaxed/simple; bh=YQS4NnULN64+SIL81o1DqBt0ehTqSsx3h0MGfL5cMjY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SZjVQnEvAXBZJZM3Ygt1WuAyIByixQhI/UvMwePL5QES2fMDcnjAkkz29jzO2FbPKUQC+2qm9HEZCxNzNSbVs2jWHaRze8wtHqNVE+Oh/JtFMhF0vN4R3+TCoQBrf7sgd+kxm8AnPSgeTx4fWbc9eFB3bU68bvvI88oZ1MYqER0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=EH4D4dPR; 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="EH4D4dPR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 34475C4CEE5; Tue, 8 Apr 2025 12:46:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744116399; bh=YQS4NnULN64+SIL81o1DqBt0ehTqSsx3h0MGfL5cMjY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EH4D4dPRN0SiI3aQvzpCuZHWaOjBLB0X4Ol9Qu2kkiJy5E6GVGa8Westk/jvEqT7L Dh76PQuz9JcKyj8CXepVNDgnn7L6xIokX3P7mdKdIz5rj/WNE5TR+jIxYituiNcfl2 /dUiUCYWw3bTBieGN5XaehXP1VXHSImT41im+wbM= 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 6.12 125/423] bpf: Use preempt_count() directly in bpf_send_signal_common() Date: Tue, 8 Apr 2025 12:47:31 +0200 Message-ID: <20250408104848.638628024@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250408104845.675475678@linuxfoundation.org> References: <20250408104845.675475678@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-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 449efaaa387a6..55f279ddfd63d 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -833,7 +833,7 @@ 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