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 CF01B267B7F; Tue, 8 Apr 2025 11:00:43 +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=1744110043; cv=none; b=VhqNnsvzurm5QYx+Z2ujl3JJitIdUMqHnDQJBsm9twsW4uyQSgaZDvyAdt9t9OsM3Um5Q9e+L4YPhdGM4Jd59oU++NifRTJWJN0QSiqfQf6Gq+Y1ajydz4GRYS0lMSIlwR9+8BrCNHGbOwIVgazZcLnwkVExRcqj3UWDwZt4XPo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744110043; c=relaxed/simple; bh=NJ5pCYUfpoSPXUCUDo5NscjOI6nse0qDRQp/+QF5kF4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gN4LgK+w1BSYv9ZlbJ/Zeiv+3a4NDhr7uUhtqQE5tnyCyz6+iG1KXRya7zGzK7FDpZP67hZIiiRibdXIPQxr+/ynmcp5+C9Tm0OqnntkjqDbf+wMGvpCNqNSIARem3HymjaGAFFeSXDUM0Wq3hdaItS4txDv7xTFqXGoX3fysCE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VKTJ4r9c; 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="VKTJ4r9c" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5ACACC4CEF1; Tue, 8 Apr 2025 11:00:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744110043; bh=NJ5pCYUfpoSPXUCUDo5NscjOI6nse0qDRQp/+QF5kF4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VKTJ4r9cV9jSiQyIp/OmXJMH3ok3odom6jHYIev3ADLNTAtyp4Kzbr2ZsZRscyNf/ gXwvU55os9xwajWOGhiIGXOiQLbE87SNwWWxulO1kGStroTz/bhVwGBT4ix3dqF6jV SdZTFK/1TRNqLoNDbjLOSuEKMWz1VqGJt2LzdmiQ= 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 5.10 147/227] bpf: Use preempt_count() directly in bpf_send_signal_common() Date: Tue, 8 Apr 2025 12:48:45 +0200 Message-ID: <20250408104824.725197514@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250408104820.353768086@linuxfoundation.org> References: <20250408104820.353768086@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 5.10-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 1656a7d9bb697..6957381b139ce 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1081,7 +1081,7 @@ 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