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Tue, 03 Mar 2020 19:26:19 -0800 Received: from mtkmbs07n1.mediatek.inc (172.21.101.16) by MTKMBS62N1.mediatek.inc (172.29.193.41) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Tue, 3 Mar 2020 19:17:09 -0800 Received: from MTKCAS06.mediatek.inc (172.21.101.30) by mtkmbs07n1.mediatek.inc (172.21.101.16) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Wed, 4 Mar 2020 11:15:20 +0800 Received: from [172.21.77.33] (172.21.77.33) by MTKCAS06.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Wed, 4 Mar 2020 11:13:44 +0800 Message-ID: <1583291775.12083.59.camel@mtkswgap22> Subject: Re: [PATCH] xhci-mtk: Fix NULL pointer dereference with xhci_irq() for shared_hcd From: Macpaul Lin To: Mathias Nyman Date: Wed, 4 Mar 2020 11:16:15 +0800 In-Reply-To: <39ec1610-1686-6509-02ac-6e73d8be2453@linux.intel.com> References: <1579246910-22736-1-git-send-email-macpaul.lin@mediatek.com> <08f69bab-2ada-d6ab-7bf7-d960e9f148a0@linux.intel.com> <1580556039.10835.3.camel@mtkswgap22> <39ec1610-1686-6509-02ac-6e73d8be2453@linux.intel.com> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200303_192624_133271_D3FA278D X-CRM114-Status: GOOD ( 23.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sriharsha Allenki , wsd_upstream , Mathias Nyman , Greg Kroah-Hartman , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Chunfeng Yun =?UTF-8?Q?=28=E4=BA=91=E6=98=A5=E5=B3=B0=29?= , "linux-mediatek@lists.infradead.org" , Matthias Brugger , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 2020-02-04 at 17:44 +0800, Mathias Nyman wrote: > On 1.2.2020 13.20, Macpaul Lin wrote: > > On Fri, 2020-01-31 at 16:50 +0200, Mathias Nyman wrote: > >> On 17.1.2020 9.41, Macpaul Lin wrote: > >>> According to NULL pointer fix: https://tinyurl.com/uqft5ra > >>> xhci: Fix NULL pointer dereference with xhci_irq() for shared_hcd > >>> The similar issue has also been found in QC activities in Mediatek. > >>> > >>> Here quote the description from the referenced patch as follows. > >>> "Commit ("f068090426ea xhci: Fix leaking USB3 shared_hcd > >>> at xhci removal") sets xhci_shared_hcd to NULL without > >>> stopping xhci host. This results into a race condition > >>> where shared_hcd (super speed roothub) related interrupts > >>> are being handled with xhci_irq happens when the > >>> xhci_plat_remove is called and shared_hcd is set to NULL. > >>> Fix this by setting the shared_hcd to NULL only after the > >>> controller is halted and no interrupts are generated." > >>> > >>> Signed-off-by: Sriharsha Allenki > >>> Signed-off-by: Macpaul Lin > >>> --- > >>> drivers/usb/host/xhci-mtk.c | 2 +- > >>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>> > >>> diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c > >>> index b18a6baef204..c227c67f5dc5 100644 > >>> --- a/drivers/usb/host/xhci-mtk.c > >>> +++ b/drivers/usb/host/xhci-mtk.c > >>> @@ -593,11 +593,11 @@ static int xhci_mtk_remove(struct platform_device *dev) > >>> struct usb_hcd *shared_hcd = xhci->shared_hcd; > >>> > >>> usb_remove_hcd(shared_hcd); > >>> - xhci->shared_hcd = NULL; > >>> device_init_wakeup(&dev->dev, false); > >>> > >>> usb_remove_hcd(hcd); > >>> usb_put_hcd(shared_hcd); > >>> + xhci->shared_hcd = NULL; > >>> usb_put_hcd(hcd); > >>> xhci_mtk_sch_exit(mtk); > >>> xhci_mtk_clks_disable(mtk); > >>> > >> > >> Could you share details of the NULL pointer dereference, (backtrace). > > > > This bug was found by our QA staff while doing 500 times plug-in and > > plug-out devices. The backtrace I have was recorded by QA and I didn't > > reproduce this issue on my own environment. However, after applied this > > patch the issue seems resolve. Here is the backtrace: > > > > Exception Class: Kernel (KE) > > PC is at [] xhci_irq+0x728/0x2364 > > LR is at [] xhci_irq+0x2f0/0x2364 > > > > Current Executing Process: > > [iptables, 859][netdagent, 770] > > > > Backtrace: > > [] __atomic_notifier_call_chain+0xa8/0x130 > > [] notify_die+0x84/0xac > > [] die+0x1d8/0x3b8 > > [] __do_kernel_fault+0x178/0x188 > > [] do_page_fault+0x44/0x3b0 > > [] do_translation_fault+0x44/0x98 > > [] do_mem_abort+0x4c/0x128 > > [] el1_da+0x24/0x3c > > [] xhci_irq+0x728/0x2364 > > [] usb_hcd_irq+0x2c/0x44 > > [] __handle_irq_event_percpu+0x26c/0x4a4 > > [] handle_irq_event+0x5c/0xd0 > > [] handle_fasteoi_irq+0x10c/0x1e0 > > [] __handle_domain_irq+0x32c/0x738 > > [] gic_handle_irq+0x174/0x1c4 > > [] el0_irq_naked+0x50/0x5c > > [] 0xffffffffffffffff > > > > Thanks, > Could you help me find out which line of code xhci_irq+0x728 is in your case. > > As Guenter pointed out there is a risk of turning the NULL pointer dereference > into a use after free if we just solve this by setting xhci->shared_hcd = NULL > later. > > If you still have that kernel around, and xhci is compiled in: > gdb vmlinux > gdb li *(xhci_irq+0x728) > Sorry that I couldn't get back to you soon. The internal code version for this issue was really old and a little bit difficult to rewind to that version. However, I think the following dump might be correct for the code base. (gdb) li *(xhci_irq+0x728) 0xffffff8008cc8634 is in xhci_irq (*stripped* kernel-4.14/drivers/usb/host/xhci.h:1694). 1689 */ 1690 #define XHCI_MAX_REXIT_TIMEOUT_MS 20 1691 1692 static inline unsigned int hcd_index(struct usb_hcd *hcd) 1693 { 1694 if (hcd->speed >= HCD_USB3) 1695 return 0; 1696 else 1697 return 1; 1698 } (gdb) Thanks Macpaul Lin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel