Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751728AbdLJWPw (ORCPT ); Sun, 10 Dec 2017 17:15:52 -0500 Received: from s18231873.onlinehome-server.info ([217.160.179.168]:33486 "EHLO godking.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751137AbdLJWPs (ORCPT ); Sun, 10 Dec 2017 17:15:48 -0500 From: Alexander Kappner To: agk@godking.net Cc: Mathias Nyman , Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] xhci: Fix use-after-free in xhci debugfs Date: Sun, 10 Dec 2017 14:14:58 -0800 Message-Id: <1512944098-4673-1-git-send-email-agk@godking.net> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6501 Lines: 147 Trying to read from debugfs after the system has resumed from hibernate causes a use-after-free and thus a protection fault. Steps to reproduce: Hibernate system, resume from hibernate, then run $ cat /sys/kernel/debug/usb/xhci/*/command-ring/enqueue dmesg below: [ 3902.765086] general protection fault: 0000 [#1] PREEMPT SMP [ 3902.765095] Modules linked in: ipheth nvidia_modeset(PO) iwlmvm mac80211 nvidia(PO) iwlwifi qmi_wwan cfg80211 thinkpad_acpi rfkill [ 3902.765118] CPU: 4 PID: 3591 Comm: cat Tainted: P O 4.14.0.1-12769-g1deab8c #1 [ 3902.765121] Hardware name: LENOVO 20ENCTO1WW/20ENCTO1WW, BIOS N1EET62W (1.35 ) 11/10/2016 [ 3902.765125] task: ffff88100263d040 task.stack: ffffc90006e50000 [ 3902.765136] RIP: 0010:xhci_trb_virt_to_dma.part.50+0x5/0x30 [ 3902.765140] RSP: 0018:ffffc90006e53da8 EFLAGS: 00010286 [ 3902.765144] RAX: ffff88100a57e680 RBX: ffff8810032f1900 RCX: ffff881013800900 [ 3902.765147] RDX: 0000000000000000 RSI: ffff881000abf488 RDI: 0d0c0a0bb1637008 [ 3902.765151] RBP: ffffc90006e53f00 R08: 0000000000000000 R09: 0000000000000000 [ 3902.765154] R10: 00007ffcd73165e0 R11: ffff88100263d040 R12: ffff880bd5afcc00 [ 3902.765157] R13: 0000000000020000 R14: 0000000000000001 R15: ffff8810032f1900 [ 3902.765161] FS: 00007f6aa6cec700(0000) GS:ffff881053d00000(0000) knlGS:0000000000000000 [ 3902.765165] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3902.765168] CR2: 00007f6aa6d08008 CR3: 00000010033f9003 CR4: 00000000003606e0 [ 3902.765172] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 3902.765175] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 3902.765178] Call Trace: [ 3902.765188] xhci_ring_enqueue_show+0x1e/0x40 [ 3902.765197] seq_read+0xdb/0x3a0 [ 3902.765204] ? __handle_mm_fault+0x5fb/0x1210 [ 3902.765211] full_proxy_read+0x4a/0x70 [ 3902.765219] __vfs_read+0x23/0x120 [ 3902.765228] vfs_read+0x8e/0x130 [ 3902.765235] SyS_read+0x42/0x90 [ 3902.765242] do_syscall_64+0x6b/0x290 [ 3902.765251] entry_SYSCALL64_slow_path+0x25/0x25 [ 3902.765256] RIP: 0033:0x7f6aa683cba0 [ 3902.765260] RSP: 002b:00007ffcd7316818 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [ 3902.765264] RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f6aa683cba0 [ 3902.765267] RDX: 0000000000020000 RSI: 00007f6aa6d09000 RDI: 0000000000000003 [ 3902.765270] RBP: 0000000000020000 R08: 00000000ffffffff R09: 0000000000000000 [ 3902.765274] R10: 00007ffcd73165e0 R11: 0000000000000246 R12: 00007f6aa6d09000 [ 3902.765277] R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000020000 [ 3902.765282] Code: 0f 44 c0 49 8b 04 24 52 48 c7 c2 30 cd cb 81 48 8d b0 98 00 00 00 31 c0 e8 39 e6 dc ff 58 e9 75 ff ff ff 0f 1f 00 0f 1f 44 00 00 <48> 8b 17 31 c0 48 39 f2 77 13 48 29 d6 48 81 fe ff 0f 00 00 77 [ 3902.765371] RIP: xhci_trb_virt_to_dma.part.50+0x5/0x30 RSP: ffffc90006e53da8 [ 3902.765376] ---[ end trace 9ee53de1dccf7d8e ]--- The issue is caused by the xhci ring structures being reallocated when the system is resumed, but pointers to the old structures being retained in the debugfs files "private" field: (gdb) list *(xhci_ring_enqueue_show+0x1e) 0xffffffff8170403e is in xhci_ring_enqueue_show (drivers/usb/host/xhci-debugfs.c:168). 163 { 164 dma_addr_t dma; 165 struct xhci_ring *ring = s->private; 166 167 dma = xhci_trb_virt_to_dma(ring->enq_seg, ring->enqueue); 168 seq_printf(s, "%pad\n", &dma); 169 170 return 0; 171 } 172 The proposed patch fixes this issue by storing a pointer to the xhci_ring field in the xhci device structure in debugfs rather than directly storing a pointer to the xhci_ring. Signed-off-by: Alexander Kappner --- drivers/usb/host/xhci-debugfs.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/drivers/usb/host/xhci-debugfs.c b/drivers/usb/host/xhci-debugfs.c index 4f7895d..60aa30a 100644 --- a/drivers/usb/host/xhci-debugfs.c +++ b/drivers/usb/host/xhci-debugfs.c @@ -162,7 +162,7 @@ static void xhci_debugfs_extcap_regset(struct xhci_hcd *xhci, int cap_id, static int xhci_ring_enqueue_show(struct seq_file *s, void *unused) { dma_addr_t dma; - struct xhci_ring *ring = s->private; + struct xhci_ring *ring = *(struct xhci_ring **)s->private; dma = xhci_trb_virt_to_dma(ring->enq_seg, ring->enqueue); seq_printf(s, "%pad\n", &dma); @@ -173,7 +173,7 @@ static int xhci_ring_enqueue_show(struct seq_file *s, void *unused) static int xhci_ring_dequeue_show(struct seq_file *s, void *unused) { dma_addr_t dma; - struct xhci_ring *ring = s->private; + struct xhci_ring *ring = *(struct xhci_ring **)s->private; dma = xhci_trb_virt_to_dma(ring->deq_seg, ring->dequeue); seq_printf(s, "%pad\n", &dma); @@ -183,7 +183,7 @@ static int xhci_ring_dequeue_show(struct seq_file *s, void *unused) static int xhci_ring_cycle_show(struct seq_file *s, void *unused) { - struct xhci_ring *ring = s->private; + struct xhci_ring *ring = *(struct xhci_ring **)s->private; seq_printf(s, "%d\n", ring->cycle_state); @@ -346,7 +346,7 @@ static void xhci_debugfs_create_files(struct xhci_hcd *xhci, } static struct dentry *xhci_debugfs_create_ring_dir(struct xhci_hcd *xhci, - struct xhci_ring *ring, + struct xhci_ring **ring, const char *name, struct dentry *parent) { @@ -387,7 +387,7 @@ void xhci_debugfs_create_endpoint(struct xhci_hcd *xhci, snprintf(epriv->name, sizeof(epriv->name), "ep%02d", ep_index); epriv->root = xhci_debugfs_create_ring_dir(xhci, - dev->eps[ep_index].new_ring, + &dev->eps[ep_index].new_ring, epriv->name, spriv->root); spriv->eps[ep_index] = epriv; @@ -423,7 +423,7 @@ void xhci_debugfs_create_slot(struct xhci_hcd *xhci, int slot_id) priv->dev = dev; dev->debugfs_private = priv; - xhci_debugfs_create_ring_dir(xhci, dev->eps[0].ring, + xhci_debugfs_create_ring_dir(xhci, &dev->eps[0].ring, "ep00", priv->root); xhci_debugfs_create_context_files(xhci, priv->root, slot_id); @@ -488,11 +488,11 @@ void xhci_debugfs_init(struct xhci_hcd *xhci) ARRAY_SIZE(xhci_extcap_dbc), "reg-ext-dbc"); - xhci_debugfs_create_ring_dir(xhci, xhci->cmd_ring, + xhci_debugfs_create_ring_dir(xhci, &xhci->cmd_ring, "command-ring", xhci->debugfs_root); - xhci_debugfs_create_ring_dir(xhci, xhci->event_ring, + xhci_debugfs_create_ring_dir(xhci, &xhci->event_ring, "event-ring", xhci->debugfs_root); -- 2.1.4