From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 53E0CC2D0A8 for ; Mon, 28 Sep 2020 10:35:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A4C30206F4 for ; Mon, 28 Sep 2020 10:35:24 +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 A4C30206F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=zx2c4.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CE6A86B005D; Mon, 28 Sep 2020 06:35:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C93F06B0062; Mon, 28 Sep 2020 06:35:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BAA476B0068; Mon, 28 Sep 2020 06:35:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0168.hostedemail.com [216.40.44.168]) by kanga.kvack.org (Postfix) with ESMTP id A53DA6B005D for ; Mon, 28 Sep 2020 06:35:23 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 62E57282D for ; Mon, 28 Sep 2020 10:35:23 +0000 (UTC) X-FDA: 77312113326.01.spade82_5f11c1d27180 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin01.hostedemail.com (Postfix) with ESMTP id 383F11004BE5E for ; Mon, 28 Sep 2020 10:35:23 +0000 (UTC) X-HE-Tag: spade82_5f11c1d27180 X-Filterd-Recvd-Size: 4681 Received: from mail.zx2c4.com (mail.zx2c4.com [192.95.5.64]) by imf15.hostedemail.com (Postfix) with ESMTP for ; Mon, 28 Sep 2020 10:35:22 +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 Cc: torvalds@linux-foundation.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, chris@chris-wilson.co.uk, akpm@linux-foundation.org, "Jason A. Donenfeld" 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 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000419, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 ) 08/0= 6/2020 Workqueue: i915-userptr-acquire __i915_gem_userptr_get_pages_worker [i9= 15] 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 0= 1 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:00000000000= 00000 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 --- 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, } =20 if (flags & FOLL_PIN) - atomic_set(¤t->mm->has_pinned, 1); + atomic_set(&mm->has_pinned, 1); =20 /* * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior --=20 2.28.0