From patchwork Mon Nov 4 23:17:13 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jann Horn X-Patchwork-Id: 13862208 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 61652D1CA09 for ; Mon, 4 Nov 2024 23:17:26 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id DB2BF10E102; Mon, 4 Nov 2024 23:17:25 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.b="e0rV5TRC"; dkim-atps=neutral Received: from mail-lf1-f45.google.com (mail-lf1-f45.google.com [209.85.167.45]) by gabe.freedesktop.org (Postfix) with ESMTPS id 183C410E102 for ; Mon, 4 Nov 2024 23:17:25 +0000 (UTC) Received: by mail-lf1-f45.google.com with SMTP id 2adb3069b0e04-539e66ba398so7184e87.0 for ; Mon, 04 Nov 2024 15:17:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1730762243; x=1731367043; darn=lists.freedesktop.org; h=cc:to:message-id:content-transfer-encoding:mime-version:subject :date:from:from:to:cc:subject:date:message-id:reply-to; bh=C+C6vlnHeSVvVkAhnAvYZvBc/e3gvFa0iQn0Z/kaiHY=; b=e0rV5TRC/9edUZBCul0oul61vsXGeSWhB5CA5l+Dun+Sjx5TOoMCCn4gYCv2gaPWLP gxPPTfF7cRU9mQCLG4O5wEj9iEYc1UdvZwJoFUhffOvXlal+2WovbSiuPHM3RUd/SpQf MzI3/56YBKfvkMTd1eThkzjpK328HDLFJ5rTpgEnFZtmi46avo4elZ65DM6ZDRmNiMoW OfKkWQb920ha5maN1vdCDV+BAIyA4OxRjavLoacHhPi/AsSUDeObcCd5KVwMOhYYRK2G Yyxefd27gEBZPdUsVQdAtIUmKN0lU5fns2AhOy6yxxlZpUpUVS0q/4Aq6/oJCjMaIORa XBww== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1730762243; x=1731367043; h=cc:to:message-id:content-transfer-encoding:mime-version:subject :date:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=C+C6vlnHeSVvVkAhnAvYZvBc/e3gvFa0iQn0Z/kaiHY=; b=Suai31Xb+b47bd7Fk/1CQ0NfIzMNj2CcUzVJtj98slXuvvR4w0wZCkc47F2S13WsIY meyVyg3KRBXs590M/O/jDdkC3E0BopW+NzMAq3JeT0y3znFnltIvnbvGWqsqTNLKnNlW zQOHLvJoXJRF7vDgZTi9ZqnGyrMuQlRUSgOgeSdpO8ZuesH+zfGWFszNKlBp2yeGKT2l DMoc/rDe/2/L7XwlwjbE9zLQlse1pQjrkAV9LDmOt1TZJ1hJn8I9ZNpi98JrxaDD1PYh PLYkYbUlB+Xr5YBOv9dvWBtRR+ht735rk/6iDs/9BMbPpdFWhrVbP3O126zA6/31L2gi Lz/g== X-Gm-Message-State: AOJu0Yw6kd4FRueJ6Sy9HJPI2snyyCHflfniyc7eWPth/8HL9DKXXCP1 J4thcFcWasgdHPy2N3N5oosOmaFLkEzaPSU/JmUJECf9Rb+7XWG3DPvFz1tnOA== X-Gm-Gg: ASbGncuTDMzEs0Jhqc3B/5I5v4dyT37RRDNsn/eXwGaervczIXdR5Q4LD7VOCOL0iAw i7y0lctBeGngwSVmwKSyvG38wO7lKxXrYbGHjSCZeGc0ocwqv2Bab9Oy3FK54hwbCOeNzoaNrsw fU8Mk3MU2YMm9yx7qriumx+qxV+a+B+X4X7T8IbufJUgRBbEyEWyFSkPYK3hWJYnTQ5iNFRr4k8 lw0Z4eiPrB5kDBy0q94BFkw5Oa1qiWDwQlNxbU= X-Google-Smtp-Source: AGHT+IFyupNQLfXx+YranHHkRssLrTsWYOFuIQ9H6XVJLdSL/2mvXLDcV6a6ibc+imq0SpyMFPjB4A== X-Received: by 2002:a19:385c:0:b0:535:3d14:1313 with SMTP id 2adb3069b0e04-53d78288ecemr164650e87.0.1730762242450; Mon, 04 Nov 2024 15:17:22 -0800 (PST) Received: from localhost ([2a00:79e0:9d:4:1b91:d97b:f7c9:2b60]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-431bd9aa611sm197561295e9.34.2024.11.04.15.17.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Nov 2024 15:17:21 -0800 (PST) From: Jann Horn Date: Tue, 05 Nov 2024 00:17:13 +0100 Subject: [PATCH] drm/panthor: Be stricter about IO mapping flags MIME-Version: 1.0 Message-Id: <20241105-panthor-flush-page-fixes-v1-1-829aaf37db93@google.com> X-B4-Tracking: v=1; b=H4sIAPhVKWcC/x2LQQqAIBAAvxJ7TlDxEH0lOmStuRAabkUg/r2l4 zAzFRgLIcPYVSj4EFNOAqbvYI1L2lHRJgxWW2eMdupc0hVzUeG4OQpJEehFVgGdRN6bYdUg+1n wF3JPc2sf9dqM/2oAAAA= X-Change-ID: 20241104-panthor-flush-page-fixes-fe4202bb18c0 To: Boris Brezillon , Steven Price , Liviu Dudau Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Jann Horn X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1730762237; l=5906; i=jannh@google.com; s=20240730; h=from:subject:message-id; bh=Ey3XFB5BJjjdu6VO458bb9nDOZIaqfSG6o++hBGILgU=; b=e1AET9ub1rPovwczIXEGiw8ak+NcFCdCvq/kFg8wlwHk3fGxhvKI5uyCuRaRAPvg0uDqRn9is 2oKkaV0l9iZAwspC9DjDNRDQgflyjOga6roZX1CpGToeKDiAzc2BqoQ X-Developer-Key: i=jannh@google.com; a=ed25519; pk=AljNtGOzXeF6khBXDJVVvwSEkVDGnnZZYqfWhP1V+C8= 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" The current panthor_device_mmap_io() implementation has two issues: 1. For mapping DRM_PANTHOR_USER_FLUSH_ID_MMIO_OFFSET, panthor_device_mmap_io() bails if VM_WRITE is set, but does not clear VM_MAYWRITE. That means userspace can use mprotect() to make the mapping writable later on. This is a classic Linux driver gotcha. I don't think this actually has any impact in practice: When the GPU is powered, writes to the FLUSH_ID seem to be ignored; and when the GPU is not powered, the dummy_latest_flush page provided by the driver is deliberately designed to not do any flushes, so the only thing writing to the dummy_latest_flush could achieve would be to make *more* flushes happen. 2. panthor_device_mmap_io() does not block MAP_PRIVATE mappings (which are mappings without the VM_SHARED flag). MAP_PRIVATE in combination with VM_MAYWRITE indicates that the VMA has copy-on-write semantics, which for VM_PFNMAP are semi-supported but fairly cursed. In particular, in such a mapping, the driver can only install PTEs during mmap() by calling remap_pfn_range() (because remap_pfn_range() wants to **store the physical address of the mapped physical memory into the vm_pgoff of the VMA**); installing PTEs later on with a fault handler (as panthor does) is not supported in private mappings, and so if you try to fault in such a mapping, vmf_insert_pfn_prot() splats when it hits a BUG() check. Fix it by clearing the VM_MAYWRITE flag (userspace writing to the FLUSH_ID doesn't make sense) and requiring VM_SHARED (copy-on-write semantics for the FLUSH_ID don't make sense). Reproducers for both scenarios are in the notes of my patch on the mailing list; I tested that these bugs exist on a Rock 5B machine. Note that I only compile-tested the patch, I haven't tested it; I don't have a working kernel build setup for the test machine yet. Please test it before applying it. Cc: stable@vger.kernel.org Fixes: 5fe909cae118 ("drm/panthor: Add the device logical block") Signed-off-by: Jann Horn Reviewed-by: Boris Brezillon Reviewed-by: Liviu Dudau --- First testcase (can write to the FLUSH_ID): ``` typeof(x) __res = (x); \ if (__res == (typeof(x))-1) \ err(1, "SYSCHK(" #x ")"); \ __res; \ }) int main(void) { int fd = SYSCHK(open(GPU_PATH, O_RDWR)); // sanity-check that PROT_WRITE+MAP_SHARED fails void *mmap_write_res = mmap(NULL, 0x1000, PROT_READ|PROT_WRITE, MAP_SHARED, fd, DRM_PANTHOR_USER_FLUSH_ID_MMIO_OFFSET); if (mmap_write_res == MAP_FAILED) { perror("mmap() with PROT_WRITE+MAP_SHARED failed as expected"); } else { errx(1, "mmap() with PROT_WRITE+MAP_SHARED worked???"); } // make a PROT_READ+MAP_SHARED mapping, and upgrade it to writable void *mmio_page = SYSCHK(mmap(NULL, 0x1000, PROT_READ, MAP_SHARED, fd, DRM_PANTHOR_USER_FLUSH_ID_MMIO_OFFSET)); SYSCHK(mprotect(mmio_page, 0x1000, PROT_READ|PROT_WRITE)); volatile uint32_t *flush_counter = (volatile uint32_t*)mmio_page; uint32_t last_old = -1; while (1) { uint32_t old_val = *flush_counter; *flush_counter = 1111; uint32_t new_val = *flush_counter; if (old_val != last_old) printf("flush counter: old=%u, new=%u\n", old_val, new_val); last_old = old_val; } } ``` Second testcase (triggers BUG() splat): ``` typeof(x) __res = (x); \ if (__res == (typeof(x))-1) \ err(1, "SYSCHK(" #x ")"); \ __res; \ }) int main(void) { int fd = SYSCHK(open(GPU_PATH, O_RDWR)); // make a PROT_READ+**MAP_PRIVATE** mapping void *ptr = SYSCHK(mmap(NULL, 0x1000, PROT_READ, MAP_PRIVATE, fd, DRM_PANTHOR_USER_FLUSH_ID_MMIO_OFFSET)); // trigger a read fault *(volatile char *)ptr; } ``` The second testcase splats like this: ``` [ 2918.411814] ------------[ cut here ]------------ [ 2918.411857] kernel BUG at mm/memory.c:2220! [ 2918.411955] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP [...] [ 2918.416147] CPU: 3 PID: 2934 Comm: private_user_fl Tainted: G O 6.1.43-19-rk2312 #428a0a5e6 [ 2918.417043] Hardware name: Radxa ROCK 5B (DT) [ 2918.417464] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 2918.418119] pc : vmf_insert_pfn_prot+0x40/0xe4 [ 2918.418567] lr : panthor_mmio_vm_fault+0xb0/0x12c [panthor] [...] [ 2918.425746] Call trace: [ 2918.425972] vmf_insert_pfn_prot+0x40/0xe4 [ 2918.426342] __do_fault+0x38/0x7c [ 2918.426648] __handle_mm_fault+0x404/0x6dc [ 2918.427018] handle_mm_fault+0x13c/0x18c [ 2918.427374] do_page_fault+0x194/0x33c [ 2918.427716] do_translation_fault+0x60/0x7c [ 2918.428095] do_mem_abort+0x44/0x90 [ 2918.428410] el0_da+0x40/0x68 [ 2918.428685] el0t_64_sync_handler+0x9c/0xf8 [ 2918.429067] el0t_64_sync+0x174/0x178 ``` --- drivers/gpu/drm/panthor/panthor_device.c | 4 ++++ 1 file changed, 4 insertions(+) --- base-commit: d78f0ee0406803cda8801fd5201746ccf89e5e4a change-id: 20241104-panthor-flush-page-fixes-fe4202bb18c0 diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c index 4082c8f2951dfdace7f73a24d6fe34e9e7f920eb..6fbff516c1c1f047fcb4dee17b87d8263616dc0c 100644 --- a/drivers/gpu/drm/panthor/panthor_device.c +++ b/drivers/gpu/drm/panthor/panthor_device.c @@ -390,11 +390,15 @@ int panthor_device_mmap_io(struct panthor_device *ptdev, struct vm_area_struct * { u64 offset = (u64)vma->vm_pgoff << PAGE_SHIFT; + if ((vma->vm_flags & VM_SHARED) == 0) + return -EINVAL; + switch (offset) { case DRM_PANTHOR_USER_FLUSH_ID_MMIO_OFFSET: if (vma->vm_end - vma->vm_start != PAGE_SIZE || (vma->vm_flags & (VM_WRITE | VM_EXEC))) return -EINVAL; + vm_flags_clear(vma, VM_MAYWRITE); break;