From nobody Wed Nov 27 04:31:52 2024 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 25CB6197A7F; Mon, 14 Oct 2024 11:36:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728905818; cv=none; b=mLwL837eTp6S8jUQ0mgu7kXXM3TmXLmqnOH0P5eQ0ih+DpYLdwK1BXCO94uaMg8E2C9MheGld28Wqtri2YV/YwlFT9Ty/Xs9mNCLhV/i42YmCdKwPunP2jSM3Eeh1lUWmlgyRZVsaWv6wGfSjN/tQXE9NN8eMAiXC8WMDo0TrEI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728905818; c=relaxed/simple; bh=kSJZarY2z94X+3xL5Dh3VLdVKOYPHcJphuWhWCcRZ9A=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=LHO+RUMiPiWxaHibHKZ2sAzt1uKvrlv3AhwcyNf/+vWsJ/UWThInNlxF4Vfa5FKrmEHYSaDnLnSIKXqqgy/O/2xAZWt1F+ENBBNP+kxgPCRB9Or+snayqNNbtOzooZuSmauDJgTMfCq/n7084HN0zrhkqMhqWG8Jk4c1/0kon4g= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=e8b2Ltvn; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=Vn6R1vmr; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="e8b2Ltvn"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Vn6R1vmr" From: =?utf-8?q?Thomas_Wei=C3=9Fschuh?= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1728905815; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=d1+jZEqucYiU1F2rEs1tJbHqPXnN7gfk5dJrwm4cXRU=; b=e8b2LtvnIPlQNKvndj4Eu/qNiWl60X/4jzRlIs7ARJ8gZOG0cZEYySmq+15901RaCs6uOZ c7fS1IaCXF4T1dRk+G+nQdicxvF8sgPwvm0w4dQmzhjPc29UZtZJ41Oy64Ah9iapQpkYVv XR9uP6x9h7cJOqv4pbC0WxeaxwuYPXLiYuR2ocjQMEbDAyGxddtgXeCGz/SSjeXs+c6jkS pgVqsbCRBVJaoxJU8LRcbCWtjT5ozcNH4SLec+Yyqm67m/zzY/UjTXtJMslMu6AchO1F3R S+AqtnnzIyIqGLKbr3s+fm0JgsvD+hBLspXUJotlwS0ExOCyBsS9kxDmCe3G4w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1728905815; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=d1+jZEqucYiU1F2rEs1tJbHqPXnN7gfk5dJrwm4cXRU=; b=Vn6R1vmrNroEp0fnkH67IQ2vJVD73wbv0C8JkuntWzXcp2zsldxWOHs7oTfFX++IYnQFmW ZI1Qx0qKxJdheqBA== Date: Mon, 14 Oct 2024 13:36:42 +0200 Subject: [PATCH 1/4] LoongArch: Don't crash in stack_top() for tasks without vDSO Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20241014-kunit-loongarch-v1-1-1699b2ad6099@linutronix.de> References: <20241014-kunit-loongarch-v1-0-1699b2ad6099@linutronix.de> In-Reply-To: <20241014-kunit-loongarch-v1-0-1699b2ad6099@linutronix.de> To: Huacai Chen , WANG Xuerui , Jiaxun Yang , Brendan Higgins , David Gow , Rae Moar Cc: loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, kunit-dev@googlegroups.com, =?utf-8?q?Thomas_Wei=C3=9Fschuh?= X-Developer-Signature: v=1; a=ed25519-sha256; t=1728905811; l=1878; i=thomas.weissschuh@linutronix.de; s=20240209; h=from:subject:message-id; bh=kSJZarY2z94X+3xL5Dh3VLdVKOYPHcJphuWhWCcRZ9A=; b=wW/i4s60xhVIYXXE3HBqscJ+MQg3YWy/nOdbmhVNj6ec07TysLo1111FKSVmBn+BSRNOtnXjV XAi28MJhxSWAA/KqBKJ0qNG8JLKzNPyJPXYISTIJS0oaG37P6lmza80 X-Developer-Key: i=thomas.weissschuh@linutronix.de; a=ed25519; pk=pfvxvpFUDJV2h2nY0FidLUml22uGLSjByFbM6aqQQws= Not all tasks have a vDSO mapped, for example kthreads never do. If such a task ever ends up calling stack_top(), it will derefence the NULL vdso pointer and crash. This can for example happen when using kunit: [<9000000000203874>] stack_top+0x58/0xa8 [<90000000002956cc>] arch_pick_mmap_layout+0x164/0x220 [<90000000003c284c>] kunit_vm_mmap_init+0x108/0x12c [<90000000003c1fbc>] __kunit_add_resource+0x38/0x8c [<90000000003c2704>] kunit_vm_mmap+0x88/0xc8 [<9000000000410b14>] usercopy_test_init+0xbc/0x25c [<90000000003c1db4>] kunit_try_run_case+0x5c/0x184 [<90000000003c3d54>] kunit_generic_run_threadfn_adapter+0x24/0x48 [<900000000022e4bc>] kthread+0xc8/0xd4 [<9000000000200ce8>] ret_from_kernel_thread+0xc/0xa4 Fixes: 803b0fc5c3f2 ("LoongArch: Add process management") Signed-off-by: Thomas Wei=C3=9Fschuh --- arch/loongarch/kernel/process.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/proces= s.c index f2ff8b5d591e4fd638109d2c98d75543c01a112c..6e58f65455c7ca3eae2e88ed852= c8655a6701e5c 100644 --- a/arch/loongarch/kernel/process.c +++ b/arch/loongarch/kernel/process.c @@ -293,13 +293,15 @@ unsigned long stack_top(void) { unsigned long top =3D TASK_SIZE & PAGE_MASK; =20 - /* Space for the VDSO & data page */ - top -=3D PAGE_ALIGN(current->thread.vdso->size); - top -=3D VVAR_SIZE; - - /* Space to randomize the VDSO base */ - if (current->flags & PF_RANDOMIZE) - top -=3D VDSO_RANDOMIZE_SIZE; + if (current->thread.vdso) { + /* Space for the VDSO & data page */ + top -=3D PAGE_ALIGN(current->thread.vdso->size); + top -=3D VVAR_SIZE; + + /* Space to randomize the VDSO base */ + if (current->flags & PF_RANDOMIZE) + top -=3D VDSO_RANDOMIZE_SIZE; + } =20 return top; } --=20 2.47.0