netdev - Re: [offlist] Re: Crash in netlink/sk_filter_trim

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Message-ID: <20180705073120.GU17271@n2100.armlinux.org.uk>
Date:   Thu, 5 Jul 2018 08:31:21 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Peter Robinson <pbrobinson@...il.com>
Cc:     netdev@...r.kernel.org, labbott@...hat.com,
        linux-arm-kernel@...ts.infradead.org,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [offlist] Re: Crash in netlink/sk_filter_trim_cap on ARMv7 on
 4.18rc1

On Thu, Jul 05, 2018 at 12:41:54AM +0100, Russell King - ARM Linux wrote:
> Subject says offlist, but this isn't...
> 
> On Wed, Jul 04, 2018 at 08:33:20AM +0100, Peter Robinson wrote:
> > Sorry for the delay on this from my end. I noticed there was some bpf
> > bits land in the last net fixes pull request landed Monday so I built
> > a kernel with the JIT reenabled. It seems it's improved in that the
> > completely dead no output boot has gone but the original problem that
> > arrived in the merge window still persists:
> > 
> > [   17.564142] note: systemd-udevd[194] exited with preempt_count 1
> > [   17.592739] Unable to handle kernel NULL pointer dereference at
> > virtual address 0000000c
> > [   17.601002] pgd = (ptrval)
> > [   17.603819] [0000000c] *pgd=00000000
> > [   17.607487] Internal error: Oops: 805 [#10] SMP ARM
> > [   17.612396] Modules linked in:
> > [   17.615484] CPU: 0 PID: 195 Comm: systemd-udevd Tainted: G      D
> >         4.18.0-0.rc3.git1.1.bpf1.fc29.armv7hl #1
> > [   17.626056] Hardware name: Generic AM33XX (Flattened Device Tree)
> > [   17.632198] PC is at sk_filter_trim_cap+0x218/0x2fc
> > [   17.637102] LR is at   (null)
> > [   17.640086] pc : [<c0ab03b4>]    lr : [<00000000>]    psr: 60000013
> > [   17.646384] sp : cfe1dd48  ip : 00000000  fp : 00000000
> > [   17.651635] r10: d837e000  r9 : d833be00  r8 : 00000000
> > [   17.656887] r7 : 00000001  r6 : e003d000  r5 : 00000000  r4 : 00000000
> > [   17.663447] r3 : 00000007  r2 : 00000000  r1 : 00000000  r0 : 00000000
> > [   17.670009] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> > [   17.677180] Control: 10c5387d  Table: 8fe20019  DAC: 00000051
> > [   17.682956] Process systemd-udevd (pid: 195, stack limit = 0x(ptrval))
> > [   17.689518] Stack: (0xcfe1dd48 to 0xcfe1e000)
> 
> Can you provide a full disassembly of sk_filter_trim_cap from vmlinux
> (iow, annotated with its linked address) for the above dump please -
> alternatively a new dump with matching disassembly.  Thanks.

Also probably a good idea to have bpf_jit_enable set to 2 to get a
dump of the bpf program being run, which I think for your problem,
you'll have to hack the kernel source to do that.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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