From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 5A3CA32C924; Sat, 12 Sep 2026 14:05:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789221902; cv=none; b=S6Gy/BBuK+990tze/MIPQmvXduoM2plwe/49qPnJyrZxFYsOOwc9b9Rl1xLbOuFNmT9Bd3Pu6qtt+JljQJRGGKqL5AoOxKE55BkKOG3bLaAYDWgIZOPSCO7UBRydElLuwDSoV9cFgEHZo652S3PxWWRQiBP/THbze281Lj6VahA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789221902; c=relaxed/simple; bh=/yqzfu7sra3RwigFVAI488DmvvcYnRB3oJOOW+eZR+c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=XCfXSszZo+uHKLXPknS+HiLyMlJvV8RszLPMA8bOjw+YRZqAPWKVGdXARe857DQZBlkqTg0qeYG3oFeNgDlGaLRBBi262ncw2+slSohkFZqZeiJyZdkfNkyLFClnOVyUDJJ1rLoAw6YOdKheZHWKAS7cFoaIuL3t54ysfO4E5ks= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Ra9nV8Wv; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Ra9nV8Wv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9B221F000FF; Sat, 12 Sep 2026 14:04:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789221899; bh=ehLWMFtLQayWMGYgtChtmaCwoanYPkXmdJo2du/oPWk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Ra9nV8Wv7IqdAiU34hn0UmxJGmNpO1ngBa98P+Y35mEc+ndcU41d2zxy6TIA0OBh/ DF1GnAgjs6sGtdRQ16+XXthelCMmkml2jeeMCa5zNWYYahO9nYq7/tegS5u51r2nLq 2dznb1dhv2gcco9UsVh05zbfXIRTR0GFztVso+D4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?J=C3=A9r=C3=A9my=20Jean?= , Huacai Chen Subject: [PATCH 6.6 0440/1424] LoongArch: Avoid preempt count underflow without probe Date: Sat, 12 Sep 2026 08:47:52 +0200 Message-ID: <20260912065617.138658646@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065607.279695368@linuxfoundation.org> References: <20260912065607.279695368@linuxfoundation.org> User-Agent: quilt/0.69 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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jérémy Jean commit 72ce4b24676e8b3b75376c4c559dd81c1ac52d5a upstream. LoongArch uses break 11 for the breakpoint placed after an instruction that Kprobes executes out of line. Since userspace can issue the same break instruction, do_bp() can reach kprobe_singlestep_handler() when there is no current probe. The handler actually returns false in this case, but it first calls preempt_enable_no_resched(). The corresponding preempt_disable() is done by kprobe_breakpoint_handler() on a real Kprobe hit, so it has not run here. As a result, an ordinary userspace breakpoint (code 11) underflows the current task's preempt count. This also makes in_interrupt() return true until the task schedules. One visible consequence is the socket cgroup attribution: cgroup_sk_alloc() treats the allocation as interrupt context and assigns the socket to the root cgroup. A socket opened from the SIGTRAP handler can then avoid a BPF_CGROUP_INET_SOCK_CREATE policy attached to the task's own cgroup. Return as soon as kprobe_running() reports no active probe. The same check has appeared in [PATCH v10 2/4] of the original LoongArch Kprobes series, but was dropped before the feature reached mainline. Cc: stable@vger.kernel.org Fixes: 6d4cc40fb5f5 ("LoongArch: Add kprobes support") Link: https://lore.kernel.org/loongarch/1670575981-14389-3-git-send-email-yangtiezhu@loongson.cn/ Assisted-by: Codex:gpt-5 Signed-off-by: Jérémy Jean Signed-off-by: Huacai Chen Signed-off-by: Greg Kroah-Hartman --- arch/loongarch/kernel/kprobes.c | 3 +++ 1 file changed, 3 insertions(+) --- a/arch/loongarch/kernel/kprobes.c +++ b/arch/loongarch/kernel/kprobes.c @@ -273,6 +273,9 @@ bool kprobe_singlestep_handler(struct pt struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); unsigned long addr = instruction_pointer(regs); + if (!cur) + return false; + if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) && ((unsigned long)&cur->ainsn.insn[1] == addr)) { restore_local_irqflag(kcb, regs);