From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f74.google.com (mail-ej1-f74.google.com [209.85.218.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6020E21D018 for ; Mon, 24 Feb 2025 08:45:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740386740; cv=none; b=AKant4ltg3DZ5q8ZRhCRSxDWKO8zdPzWNl/5XlCzXP0oeWVNJgfob7HX3fhDKkX7GPf4BmiHlAG1LL6K/C34N3TZ0F+S2pK5Jpow3QkVOgMdNC0UKOW0z+9iCtV8NUDd9y1yN7Ax6eSU9+7x4YQsZvPBDtdDzajK9TuE8OlVKow= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740386740; c=relaxed/simple; bh=6GQcXVe2SCy/A7R9Dn8Z5XgQUnXLIPESvvaPTN/8lhk=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=SndITBd89UM9aTZmZX+OWjf+c6TA/c5G8GK9/b5rq9wVo6wDGzQ1HxMqLRP81Q5c6Q355AUAyAkOlXvL/YVb6oLxjuVehFpXdoPNsrhHkWeDHuWL/5Ik6GX7cx4Gy886iRTD5EPOOyYlTp25gCuC0vOX0zXlgOZ0lfO/AXZU1sU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--dvyukov.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=VtP9LqDu; arc=none smtp.client-ip=209.85.218.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--dvyukov.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="VtP9LqDu" Received: by mail-ej1-f74.google.com with SMTP id a640c23a62f3a-abb4d3ef1a7so349856866b.3 for ; Mon, 24 Feb 2025 00:45:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1740386737; x=1740991537; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=3mGUzlKU/88ScEoKu5QKXimL46RVCUcRx5GeW41a5LQ=; b=VtP9LqDuxePPrPapWBhU6u3Nh6Z3UATUNNoTwPkxNYnF0BdL1biSDxtAg2NtMSBaSL 4lgYhD+NarS8hqnonZvKqfPHAhBjn6Q8iIuO1zq6WMLgJsa74gX3OMXMrJ+e85pA5kDb +DqshtgMHO4y3iy6YFa7gs88T5IAZRECmJisyzJOi73mWo4H2v2w6nXtGWGIDnKf6Twi nJEIrf6qWZN5bWvvmrrjmscI/Vrx8D31csMmNwqN+SI2YprHkBkClInpZzy2cIOpkFVw r2gLWXGJ3SGBbz+UyTdO/MgDmHob37MC5zkMI4gfWTM/It8GdRLoXi7fTPiPu3VYAjKL QmaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740386737; x=1740991537; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=3mGUzlKU/88ScEoKu5QKXimL46RVCUcRx5GeW41a5LQ=; b=BRgy4KWas+8TGjYprg8+UhPj81Oz8ux3DHqGorKuBfMh2XRvFSbr4FCbUUntPGFOXz W8q0aF4AUnv1LzLNyh5oKYZSP/lGDOlB03kn7L4x6YyeaN5jaj6o29Gohjt3AYy6Ddu5 EAIHg4O0LL8D1s6+7OT+KacRHwiG0GSp/PS7aVdu3iFfSFtQ6kI/7LBdo+ZHdGZGWa2y zDVjJNL6/kFuQ9kzd3b/p4Uf1Cxv9w8fw0azpFjzHS1b8CM65J3IW5pPQXd3hwo99/nG bJxW586eIYP8eQ07SjAPkuqV6aitmscNiXSEnkbs0M9my5P2+NRhuco/ApJCO2BuhOHT aOxQ== X-Forwarded-Encrypted: i=1; AJvYcCWJMBM2DeIWkiIhYMECE9TBmDMbRtc0O9kz5EknFj7eXHSrqKrdnfmnBdcbMAQbWtazdXN6mNtIiV0FFPM=@vger.kernel.org X-Gm-Message-State: AOJu0Yx9S7QVOtr6rSiGL8VGTpPTJzwdCbgsxpJp27nXAl54WD/XcebS TFYQq/qYFnv+5PUQT2DArFR6kkOabMLHk8x4Kv0CpkcX6MPKyORj1bfDriERHeZE9FSYP1rnxwU GQ8fZig== X-Google-Smtp-Source: AGHT+IFukiwuqJxcfOF08YHnGZAmuqGLDYsPVBtSaYDroQXCGE5fxa9Wcxt1IHW+nQHGDLsYZPveaU//aLN+ X-Received: from ejcrt7.prod.google.com ([2002:a17:907:8947:b0:abb:910b:456d]) (user=dvyukov job=prod-delivery.src-stubby-dispatcher) by 2002:a17:906:c456:b0:abc:269d:d534 with SMTP id a640c23a62f3a-abc269dd58dmr789993966b.40.1740386736737; Mon, 24 Feb 2025 00:45:36 -0800 (PST) Date: Mon, 24 Feb 2025 09:45:25 +0100 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: X-Mailer: git-send-email 2.48.1.601.g30ceb7b040-goog Message-ID: Subject: [PATCH v2 1/3] syscall_user_dispatch: Allow allowed range wrap-around From: Dmitry Vyukov To: krisman@collabora.com, tglx@linutronix.de, luto@kernel.org, peterz@infradead.org, keescook@chromium.org, gregory.price@memverge.com Cc: Dmitry Vyukov , Marco Elver , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" There are two possible scenarios for syscall filtering: - having a trusted/allowed range of PCs, and intercepting everything else - or the opposite: a single untrusted/intercepted range and allowing everything else The current implementation only allows the former use case due to allowed range wrap-around check. Allow the latter use case as well by removing the wrap-around check. The latter use case is relevant for any kind of sandboxing scenario, or monitoring behavior of a single library. If a program wants to intercept syscalls for PC range [START, END) then it needs to call: prctl(..., END, -(END-START), ...); which sets a wrap-around range that excludes everything besides [START, END). Signed-off-by: Dmitry Vyukov Cc: Gabriel Krisman Bertazi Cc: Thomas Gleixner Cc: Andy Lutomirski Cc: Peter Zijlstra (Intel) Cc: Kees Cook Cc: Gregory Price Cc: Marco Elver Cc: linux-kernel@vger.kernel.org --- kernel/entry/syscall_user_dispatch.c | 9 +++------ kernel/sys.c | 6 ++++++ 2 files changed, 9 insertions(+), 6 deletions(-) diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c index 5340c5aa89e7d..a0659f0515404 100644 --- a/kernel/entry/syscall_user_dispatch.c +++ b/kernel/entry/syscall_user_dispatch.c @@ -37,6 +37,7 @@ bool syscall_user_dispatch(struct pt_regs *regs) struct syscall_user_dispatch *sd = ¤t->syscall_dispatch; char state; + /* Note: this check form allows for range wrap-around. */ if (likely(instruction_pointer(regs) - sd->offset < sd->len)) return false; @@ -80,13 +81,9 @@ static int task_set_syscall_user_dispatch(struct task_struct *task, unsigned lon break; case PR_SYS_DISPATCH_ON: /* - * Validate the direct dispatcher region just for basic - * sanity against overflow and a 0-sized dispatcher - * region. If the user is able to submit a syscall from - * an address, that address is obviously valid. + * Note: we don't check and allow arbitrary values for + * offset/len in particular to allow range wrap-around. */ - if (offset && offset + len <= offset) - return -EINVAL; /* * access_ok() will clear memory tags for tagged addresses diff --git a/kernel/sys.c b/kernel/sys.c index cb366ff8703af..666322026ad72 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2735,6 +2735,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, error = (current->flags & PR_IO_FLUSHER) == PR_IO_FLUSHER; break; case PR_SET_SYSCALL_USER_DISPATCH: + /* + * Sign-extend len for 32-bit processes to allow region + * wrap-around. + */ + if (in_compat_syscall()) + arg4 = (long)(s32)arg4; error = set_syscall_user_dispatch(arg2, arg3, arg4, (char __user *) arg5); break; -- 2.48.1.601.g30ceb7b040-goog