From patchwork Mon Sep 28 10:35:07 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 11805021 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4F806618 for ; Tue, 29 Sep 2020 07:14:11 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 26BD320754 for ; Tue, 29 Sep 2020 07:14:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="J5yqMS89" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 26BD320754 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=zx2c4.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id F2B1A6E455; Tue, 29 Sep 2020 07:13:59 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail.zx2c4.com (mail.zx2c4.com [192.95.5.64]) by gabe.freedesktop.org (Postfix) with ESMTPS id 14F3689C17; Mon, 28 Sep 2020 10:35:23 +0000 (UTC) Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTP id ed9f277a; Mon, 28 Sep 2020 10:03:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=zx2c4.com; h=from:to:cc :subject:date:message-id:in-reply-to:references:mime-version :content-transfer-encoding; s=mail; bh=4eS4KVw+eff75q2oQykBpqEjw NI=; b=J5yqMS89hgyMX0QziV8GupKGPwxrxPZdhMy/7aytvT9d+N8JOimRlW8KT wdpl1ZRiMGXCdDolMdjHdNJZlj+UdT8S5Hc+1rm//VJctpRIgNkE1fyDPRhWFpVl GibowlW8lNe84FWuMuKzshEZfNSI+eCtDq8fr2kmXH9rBV8ic7wR18GCh3dXXKf/ rebuZKy2hxmkvZckpi0ZfTpItF41zFPfbyV6dONaXfTkyKlow0c26VvbN94SFiiO i0c/CZiQkTmkD+pBYbJ9zgGCiH+nBTfo1oQAXcatB1v4ICGWxH6LCoLCAEH1iRsk xqmgddiFjrMNaJxO/PytBuXSevMjg== Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 782f82a2 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Mon, 28 Sep 2020 10:03:55 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-mm@kvack.org, peterx@redhat.com, jgg@ziepe.ca Subject: [PATCH] mm: do not rely on mm == current->mm in __get_user_pages_locked Date: Mon, 28 Sep 2020 12:35:07 +0200 Message-Id: <20200928103507.2164-1-Jason@zx2c4.com> In-Reply-To: References: MIME-Version: 1.0 X-Mailman-Approved-At: Tue, 29 Sep 2020 07:12:58 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Jason A. Donenfeld" , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, chris@chris-wilson.co.uk, akpm@linux-foundation.org, torvalds@linux-foundation.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" It seems likely this block was pasted from internal_get_user_pages_fast, which is not passed an mm struct and therefore uses current's. But __get_user_pages_locked is passed an explicit mm, and current->mm is not always valid. This was hit when being called from i915, which uses: pin_user_pages_remote-> __get_user_pages_remote-> __gup_longterm_locked-> __get_user_pages_locked Before, this would lead to an OOPS: BUG: kernel NULL pointer dereference, address: 0000000000000064 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP CPU: 10 PID: 1431 Comm: kworker/u33:1 Tainted: P S U O 5.9.0-rc7+ #140 Hardware name: LENOVO 20QTCTO1WW/20QTCTO1WW, BIOS N2OET47W (1.34 ) 08/06/2020 Workqueue: i915-userptr-acquire __i915_gem_userptr_get_pages_worker [i915] RIP: 0010:__get_user_pages_remote+0xd7/0x310 Code: f5 01 00 00 83 7d 00 01 0f 85 ed 01 00 00 f7 c1 00 00 04 00 0f 84 58 01 00 00 65 48 8b 04 25 00 6d 01 00 48 8b 80 40 03 00 00 40 64 01 00 00 00 65 48 8b 04 25 00 6d 01 00 48 c7 44 24 18 00 RSP: 0018:ffff888fdfe47de0 EFLAGS: 00010206 RAX: 0000000000000000 RBX: 00007fe188531000 RCX: 0000000000040001 RDX: 0000000000000001 RSI: 00007fe188531000 RDI: ffff888ff0748f00 RBP: ffff888fdfe47e54 R08: ffff888fedc7d7c8 R09: 0000000000000000 R10: 0000000000000018 R11: fefefefefefefeff R12: ffff888ff0748f00 R13: ffff888fedc7d7c8 R14: ffff888f81fe3a40 R15: 0000000000042003 FS: 0000000000000000(0000) GS:ffff888ffc480000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000064 CR3: 0000000002009003 CR4: 00000000003706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __i915_gem_userptr_get_pages_worker+0xc8/0x260 [i915] process_one_work+0x1ca/0x390 worker_thread+0x48/0x3c0 ? rescuer_thread+0x3d0/0x3d0 kthread+0x114/0x130 ? kthread_create_worker_on_cpu+0x40/0x40 ret_from_fork+0x1f/0x30 CR2: 0000000000000064 This commit fixes the problem by using the mm pointer passed to the function rather than the bogus one in current. Fixes: 008cfe4418b3 ("mm: Introduce mm_struct.has_pinned") Cc: Jason Gunthorpe Cc: Peter Xu Signed-off-by: Jason A. Donenfeld Reviewed-by: Jason Gunthorpe --- mm/gup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/gup.c b/mm/gup.c index dfe781d2ad4c..e869c634cc9a 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1256,7 +1256,7 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm, } if (flags & FOLL_PIN) - atomic_set(¤t->mm->has_pinned, 1); + atomic_set(&mm->has_pinned, 1); /* * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior