From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793209862; b=RuLsTpBFv1bs6t31w8Uok+ZZU/uZWZ9FLG/FuxxiIhhZgi4PptQFBJon1G/JwtjtudPm I62kU2i7wEQqPoXGVdbFi3TinEic4bWvVcpTjWPbCB+j0mv1+mbK8qRe/EZI2dhY4iomu GBr0xKTLBL7EZFsS2iygGAq3dgMYDYu1lBDc7HmhKEFU6gVZ+AtxcJNYdWDQSTZ03/wKz ZhqfnOSe13FQ5uV6opICdkreUPWmD3WA8q+S+YbX5l4I/ALVFxkY028m+OcU58CioxIR3 6jGewc1a5tOvOHrrbb6iCiXRQOSu1lSbc+8Eu0VRkMkHXiY4N7T0n5DsJjeNTstsLdg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793209862; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=WHRlOYelGqk4TJxwMNW4nvM/jzbwjGUbYrptz/VeSDs=; b=VDSJ32nayBghY/rVhq6lICZS14Bq7RjCkQsxYDdkzjNx+wECJfwWSrTIsAAb+HU07NmC lVz2l/f3tBSUBj4AYqsCNtxUMz5tSmZ2tk2nUzZwZ+g75iUuQOfDIomTe2mav4uFtuL0B pXLDsIBxaBg9dLVDgY/Bk8exQ4LCVd2nZ7l++AFjd2EFine8YKhKyQA7zpWnE4HwrGMHX jZLl4Y/s8BTJZhhXT68ncw9Wvx83LAs9yKFq4zNfAetm/ufTP0rhTWzdjd17Mm/jMVGWT sBom+YG/goG60oZeE4un3Vro43dtr4CFWbJhERQ4HumgVtVsNQARf9CvrZ+E7FO8Tqg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=li6Y0dfc; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A2D6D606A31A; Wed, 28 Oct 2026 17:51:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=li6Y0dfc Received: by smtp.kernel.org (Postfix) with ESMTPSA id F18541F01825; Wed, 28 Oct 2026 17:51:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793209862; bh=WHRlOYelGqk4TJxwMNW4nvM/jzbwjGUbYrptz/VeSDs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=li6Y0dfcfPxMyGJTBgKxjpnKoauPifxVJars9hxVNqRtwy8pUMsajnaW+4PgwteZD Sm6gfAtC602EB6LWIMTqupw0LnQS7B8Dznot7cY0rSxNb66zaZtUfRYp5sh0e1O+UW QwRGzt+fJQ6s8toeqq2IrRvNHcisFMX9fjhqPIY8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Oleg Nesterov , "Christian Brauner (Amutable)" Subject: [PATCH 6.18 104/109] ptrace: refuse to change the signal mask of a user worker Date: Wed, 28 Oct 2026 18:01:28 +0100 Message-ID: <20261028165944.803744632@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165942.357251485@linuxfoundation.org> References: <20261028165942.357251485@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christian Brauner commit cabc249e6560bee7bdfee9fbcb7ce4e951dcfd41 upstream. A user worker is created with every signal other than SIGKILL and SIGSTOP blocked. It never runs user code and that mask is what keeps get_signal() from dequeuing anything else for it. complete_signal() never picks a thread that blocks the signal, tkill() queues on the worker but nothing dequeues it. ptrace_signal() requeues an injected signal that the tracee blocks. PTRACE_SETSIGMASK is the only way to change that mask from the outside. A tracer that clears it makes the worker eligible for every signal. Whatever the worker then dequeues it can only act on by leaving. Refuse PTRACE_SETSIGMASK for a user worker with -EPERM, the way ptrace_attach() refuses a kernel thread. A worker is guaranteed to only ever dequeue SIGKILL or SIGSTOP and an injected signal stays pending on it, which is what already happens when the mask isn't touched. Taking the request and quietly leaving the mask alone was the other option, the way set_current_blocked() keeps SIGKILL and SIGSTOP unblocked whatever userspace asks for. But then a tracer gets success back with nothing changed and no way to tell that apart from a mask that took effect. Fixes: e8b33b8cfafc ("Revert "kernel: treat PF_IO_WORKER like PF_KTHREAD for ptrace/signals"") Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260921-work-coredump-fixes-v3-9-8e4adb1619e6@kernel.org Acked-by: Oleg Nesterov Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Greg Kroah-Hartman --- kernel/ptrace.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -1211,6 +1211,12 @@ int ptrace_request(struct task_struct *c case PTRACE_SETSIGMASK: { sigset_t new_set; + /* A user worker only ever takes SIGKILL and SIGSTOP. */ + if (child->flags & PF_USER_WORKER) { + ret = -EPERM; + break; + } + if (addr != sizeof(sigset_t)) { ret = -EINVAL; break;