From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DBE2847D460; Mon, 5 Oct 2026 12:07:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791202050; cv=none; b=Fe2UpvqfhoHjOO2JKOid6iRxCl1cPMNQMPh0Es1pdY3G7Ks0njIvwza1U34JNlbTUBTUZ6W0uRinpaE3L6QR43E1WGpXDea3KWPZBNTZUD+aGDdwRwdJicLcExSKggwsy40cnkmTPNtJzLV4PS9BLSVExlkvfKYbBEUmiQvRn4k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791202050; c=relaxed/simple; bh=3FgcCnbV9YRK9cWAc5HYLFiWEjRwfbEEYLqixQdU520=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=G8h/yCnfjpvWzikI6ms6i4nfIIzz3fyXeisw3ZgIr61Ln/fKt5tvmtHOaDjEPyK/ATFbs+CVRmTUGyYqTJtDfo2z2wLhoGoCaPky0Wz13eHP799ptx+TmofX6eFXqWNnTwHvYHojtyeDa+YPNuEXlwt4VDqlI8WgO6E8U8cxvEA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=EJjN4Ffq; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="EJjN4Ffq" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 54873152B; Mon, 5 Oct 2026 05:07:23 -0700 (PDT) Received: from [192.168.147.49] (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A7D8D3F86F; Mon, 5 Oct 2026 05:07:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1791202046; bh=3FgcCnbV9YRK9cWAc5HYLFiWEjRwfbEEYLqixQdU520=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=EJjN4Ffqe2Y68JHHRmfhnLQ2jkZ6dkZdRpINSBf9H3ljFLGnSO/iS3BmoeQbGd2qV caYdW4R837bIczfSbfRSnS83xo8hcHgy5M+2lu4ErmrqhHNwLyHsakUcOzDv+0TMqS IFNGxJmJAcAJ3NEyprpWvdFaOk7a/oGUTtn20C0M= Message-ID: Date: Mon, 5 Oct 2026 13:07:18 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] usb: mtu3: Fix double dereference in TP_printk To: paulmck@kernel.org Cc: linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, chunfeng.yun@mediatek.com, gregkh@linuxfoundation.org, rostedt@goodmis.org, mark.rutland@arm.com References: <20260922103756.104846-1-vladimir.murzin@arm.com> <845ef1a3-8d85-4007-aa2c-05e59e79afcd@arm.com> <315259c9-d7b9-44bc-8896-ecb9429a6eb5@paulmck-laptop> Content-Language: en-GB From: Vladimir Murzin In-Reply-To: <315259c9-d7b9-44bc-8896-ecb9429a6eb5@paulmck-laptop> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi All, On 9/28/26 19:21, Paul E. McKenney wrote: > On Mon, Sep 28, 2026 at 02:11:42PM +0100, Vladimir Murzin wrote: >> Hi All, >> >> Gentle ping... spat is still present in v7.3-rc5 > If no one else wants to push it, I can do so. I gotta admit that the > resulting test failures when I forget to apply it are a bit annoying. ;-) > > Thanx, Paul > FYI, splat is still present in v7.3-rc6 :( Thanks Vladimir >> Cheers >> Vladimir >> >> On 9/22/26 11:37, Vladimir Murzin wrote: >>> Paul reported kernel splat: >>> >>> [ 0.000000] TRACE EVENT ERROR: Event mtu3_gadget_ep_set_halt has double dereference in TP_printk: &REC->gpd_ring->dma >>> [ 0.000000] ------------[ cut here ]------------ >>> [ 0.000000] Event mtu3_gadget_ep_set_halt has double dereference in TP_printk: &REC->gpd_ring->dma >>> [ 0.000000] WARNING: kernel/trace/trace_events.c:420 at test_double_dereference+0x144/0x14c, CPU#0: swapper/0/0 >>> [ 0.000000] Modules linked in: >>> [ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.3.0-rc1 #15247 PREEMPT >>> [ 0.000000] Hardware name: linux,dummy-virt (DT) >>> [ 0.000000] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) >>> [ 0.000000] pc : test_double_dereference+0x144/0x14c >>> [ 0.000000] lr : test_double_dereference+0x144/0x14c >>> [ 0.000000] sp : ffffc80aa7633bf0 >>> [ 0.000000] x29: ffffc80aa7633bf0 x28: ffffc80aa7c0f047 x27: 000508b58019388f >>> [ 0.000000] x26: 0000000000000003 x25: 0000000000000007 x24: ffffc80aa5fceff8 >>> [ 0.000000] x23: ffffc80aa7c0f05a x22: ffffc80aa64edfe8 x21: ffffc80aa7c0fce8 >>> [ 0.000000] x20: ffffc80aa7c0f047 x19: 0000000000000013 x18: 0000000000000001 >>> [ 0.000000] x17: 6572656420656c62 x16: 756f642073616820 x15: 746c61685f746573 >>> [ 0.000000] x14: 0000000000000000 x13: ffff000139d90000 x12: 0000000000000045 >>> [ 0.000000] x11: 00000000000000cf x10: ffff00013f546428 x9 : ffff000139d90000 >>> [ 0.000000] x8 : 3fffffffffffc000 x7 : 0000000000000001 x6 : 0000000000000001 >>> [ 0.000000] x5 : ffff00013f4e6440 x4 : 0000000000000000 x3 : 0000000000000000 >>> [ 0.000000] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffc80aa764a700 >>> [ 0.000000] Call trace: >>> [ 0.000000] test_double_dereference+0x144/0x14c (P) >>> [ 0.000000] trace_event_raw_init+0x37c/0x5d8 >>> [ 0.000000] event_init+0x34/0xc0 >>> [ 0.000000] trace_event_init+0xec/0x588 >>> [ 0.000000] trace_init+0x24/0x6e0 >>> [ 0.000000] start_kernel+0x4a0/0x8ec >>> [ 0.000000] __primary_switched+0x88/0x90 >>> [ 0.000000] irq event stamp: 0 >>> [ 0.000000] hardirqs last enabled at (0): [<0000000000000000>] 0x0 >>> [ 0.000000] hardirqs last disabled at (0): [<0000000000000000>] 0x0 >>> [ 0.000000] softirqs last enabled at (0): [<0000000000000000>] 0x0 >>> [ 0.000000] softirqs last disabled at (0): [<0000000000000000>] 0x0 >>> [ 0.000000] ---[ end trace 0000000000000000 ]--- >>> [ 0.000000] TRACE EVENT ERROR: Event mtu3_gadget_ep_disable has double dereference in TP_printk: &REC->gpd_ring->dma >>> [ 0.000000] TRACE EVENT ERROR: Event mtu3_gadget_ep_enable has double dereference in TP_printk: &REC->gpd_ring->dma >>> >>> Which also observed by Mark and myself. >>> >>> The splat it result of new check introduced by b5cc230af5e5 ("tracing: >>> Warn when an event dereferences a pointer in TP_printk()") which >>> correctly catches issue with %pad dereferencing the address saved in >>> the ring buffer. TP_fast_assign() logic gets executed when the >>> tracepoint is triggered, however the TP_printk() is executed when the >>> user reads the trace buffer which could be seconds, minutes, hours, >>> days, even months later and nothing guarantee that __entry->gpd_ring >>> pointer will still be pointing to what it was when it was recorded. >>> >>> Fix the issue by capturing immediate value of gpd_ring.dma when trace >>> point is triggered. >>> >>> Reported-by: Paul E. McKenney >>> Tested-by: Mark Rutland >>> Reviewed-by: Steven Rostedt >>> Signed-off-by: Vladimir Murzin >>> --- >>> drivers/usb/mtu3/mtu3_trace.h | 4 +++- >>> 1 file changed, 3 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/usb/mtu3/mtu3_trace.h b/drivers/usb/mtu3/mtu3_trace.h >>> index 89870175d635..9aaa167d69c1 100644 >>> --- a/drivers/usb/mtu3/mtu3_trace.h >>> +++ b/drivers/usb/mtu3/mtu3_trace.h >>> @@ -224,6 +224,7 @@ DECLARE_EVENT_CLASS(mtu3_log_ep, >>> __field(unsigned int, flags) >>> __field(unsigned int, direction) >>> __field(struct mtu3_gpd_ring *, gpd_ring) >>> + __field(dma_addr_t, gpd_ring_dma) >>> ), >>> TP_fast_assign( >>> __assign_str(name); >>> @@ -235,12 +236,13 @@ DECLARE_EVENT_CLASS(mtu3_log_ep, >>> __entry->flags = mep->flags; >>> __entry->direction = mep->is_in; >>> __entry->gpd_ring = &mep->gpd_ring; >>> + __entry->gpd_ring_dma = mep->gpd_ring.dma >>> ), >>> TP_printk("%s: type %s maxp %d slot %d mult %d burst %d ring %p/%pad flags %c:%c%c%c:%c", >>> __get_str(name), usb_ep_type_string(__entry->type), >>> __entry->maxp, __entry->slot, >>> __entry->mult, __entry->maxburst, >>> - __entry->gpd_ring, &__entry->gpd_ring->dma, >>> + __entry->gpd_ring, &__entry->gpd_ring_dma, >>> __entry->flags & MTU3_EP_ENABLED ? 'E' : 'e', >>> __entry->flags & MTU3_EP_STALL ? 'S' : 's', >>> __entry->flags & MTU3_EP_WEDGE ? 'W' : 'w', >>> -- 2.34.1 >>>