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 EE577268C6B; Tue, 8 Apr 2025 12:06:49 +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=1744114010; cv=none; b=EuTo2i1TiLo4ZIzp+CrsbC89ncCBvpPOhZcyGAL00opKrkJVyS/nT/f5+EAebtmLJTTpJmMpEJ6Trz30Jrk6BZTGZvJrsxh2IhM9BFajPxY7+frj/z7S0lXBksqtZ8Q8rMc2c1XcG+dqSCPjNxdJGD1nJJ4wRkugIx05at6Rt7Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744114010; c=relaxed/simple; bh=H4HR6W7JsRZs31Rlac+HtXtwcsAI3ksVRoMEjFfdS4o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ddt3lXgsQ7mVmLdb+LT/RvC/s+yQwQAuHdM3PU98HGyj8n0b5kma2uzxwy4XZE0QGwh9yCJswsmmDnYCTSn3ZsMnIXAStb/yOJ2cTvg5Twy8+13j07b0gcQLA9/8Z2zsikosmohXHShg5S0+8WB081Xhh7rQyJw8gRIMr4h69Ps= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=hNQg0AlL; 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="hNQg0AlL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 807C9C4CEE5; Tue, 8 Apr 2025 12:06:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744114009; bh=H4HR6W7JsRZs31Rlac+HtXtwcsAI3ksVRoMEjFfdS4o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hNQg0AlL6O+3qcaPoo78aZETClTb4K0CVqVJ3y5CzxGSBgFYdQ2siU9H5Zh4NQcBj tky9slomJ4JrJZ9Zt+FuWenUVIq0kNI67DKjzaFPxj0gaKgq8NusCBYrvGqRFt6Trj qX4CJ9SFAX+I244RKu/ky6jzT2wgy5SAMMMDiWtw= 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 5.4 102/154] bpf: Use preempt_count() directly in bpf_send_signal_common() Date: Tue, 8 Apr 2025 12:50:43 +0200 Message-ID: <20250408104818.599222155@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250408104815.295196624@linuxfoundation.org> References: <20250408104815.295196624@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 5.4-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 ac3125d0c73f1..75ea2ab532134 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -653,7 +653,7 @@ BPF_CALL_1(bpf_send_signal, u32, sig) 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