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Date:   Mon, 17 Aug 2020 10:44:57 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
To:     Corey Minyard <minyard@acm.org>
Cc:     linux-sctp@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: Oops on current Raspian when closing an SCTP connection
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References: <20200816230624.GB2865@minyard.net>
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On Sun, Aug 16, 2020 at 06:06:24PM -0500, Corey Minyard wrote:
> I'm seeing the following when an SCTP connection terminates.  This is on
> Raspian on a Raspberry Pi, version is Linux version 5.4.51-v7+.  That's
> 32-bit ARM.
> 
> I haven't looked into it yet, I thought I would report before trying to
> chase anything down.  I'm not seeing it on 5.4 x86_64 systems.
> 
> Aug 16 17:59:00 access kernel: [510640.326415] Unable to handle kernel NULL pointer dereference at virtual address 00000008
> Aug 16 17:59:00 access kernel: [510640.341624] pgd = c00fc16c
> Aug 16 17:59:00 access kernel: [510640.347834] [00000008] *pgd=355ef835, *pte=00000000, *ppte=00000000
> Aug 16 17:59:00 access kernel: [510640.357731] Internal error: Oops: 17 [#22] SMP ARM
> Aug 16 17:59:01 access kernel: [510640.365931] Modules linked in: md5 sctp ftdi_sio cp210x usbserial raspberrypi_hwmon bcm2835_codec(C) v4l2_mem2mem bcm2835_isp(C) bcm2835_v4l2(C) bcm2835_mmal_vchiq(C) videobuf2_vmalloc videobuf2_dma_contig videobuf2_memops videobuf2_v4l2 snd_bcm2835(C) videobuf2_common i2c_bcm2835 snd_pcm snd_timer videodev snd mc vc_sm_cma(C) uio_pdrv_genirq uio fixed nf_nat_pptp nf_conntrack_pptp nf_nat nf_conntrack nf_defrag_ipv4 rtc_ds1307 regmap_i2c i2c_dev ip_tables x_tables ipv6 nf_defrag_ipv6
> Aug 16 17:59:01 access kernel: [510640.425420] CPU: 1 PID: 4592 Comm: gtlsshd Tainted: G      D  C        5.4.51-v7+ #1327
> Aug 16 17:59:01 access kernel: [510640.438008] Hardware name: BCM2835
> Aug 16 17:59:01 access kernel: [510640.443823] PC is at sctp_ulpevent_free+0x38/0xa0 [sctp]
> Aug 16 17:59:01 access kernel: [510640.451498] LR is at sctp_queue_purge_ulpevents+0x34/0x50 [sctp]

Not ringing a bell here. Can you pinpoint on which line this crash
was? It seems, by the 0x8 offset and these function offsets, that this
could be when it was trying to access event->rmem_len, but if event
was NULL then it should have crashed earlier.

  Marcelo