linux-kernel - Re: [PATCH] iov_iter: Fix 9p virtio breakage

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Message-ID: <861s82fopo.wl-marc.zyngier@arm.com>
Date:   Sat, 03 Nov 2018 10:19:15 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     David Howells <dhowells@...hat.com>,
        <linux-kernel@...r.kernel.org>, Will Deacon <will.deacon@....com>
Subject: Re: [PATCH] iov_iter: Fix 9p virtio breakage

On Fri, 02 Nov 2018 19:04:33 +0000,
Al Viro <viro@...IV.linux.org.uk> wrote:
> 
> On Fri, Nov 02, 2018 at 05:16:51PM +0000, Marc Zyngier wrote:
> > When switching to the new iovec accessors, a negation got subtly
> > dropped, leading to 9p being remarkably broken (here with kvmtool):
> > 
> > [    7.430941] VFS: Mounted root (9p filesystem) on device 0:15.
> > [    7.432080] devtmpfs: mounted
> > [    7.432717] Freeing unused kernel memory: 1344K
> > [    7.433658] Run /virt/init as init process
> >   Warning: unable to translate guest address 0x7e00902ff000 to host
> >   Warning: unable to translate guest address 0x7e00902fefc0 to host
> >   Warning: unable to translate guest address 0x7e00902ff000 to host
> >   Warning: unable to translate guest address 0x7e008febef80 to host
> >   Warning: unable to translate guest address 0x7e008febf000 to host
> >   Warning: unable to translate guest address 0x7e008febef00 to host
> >   Warning: unable to translate guest address 0x7e008febf000 to host
> > [    7.436376] Kernel panic - not syncing: Requested init /virt/init failed (error -8).
> > [    7.437554] CPU: 29 PID: 1 Comm: swapper/0 Not tainted 4.19.0-rc8-02267-g00e23707442a #291
> > [    7.439006] Hardware name: linux,dummy-virt (DT)
> > [    7.439902] Call trace:
> > [    7.440387]  dump_backtrace+0x0/0x148
> > [    7.441104]  show_stack+0x14/0x20
> > [    7.441768]  dump_stack+0x90/0xb4
> > [    7.442425]  panic+0x120/0x27c
> > [    7.443036]  kernel_init+0xa4/0x100
> > [    7.443725]  ret_from_fork+0x10/0x18
> > [    7.444444] SMP: stopping secondary CPUs
> > [    7.445391] Kernel Offset: disabled
> > [    7.446169] CPU features: 0x0,23000438
> > [    7.446974] Memory Limit: none
> > [    7.447645] ---[ end Kernel panic - not syncing: Requested init /virt/init failed (error -8). ]---
> > 
> > Restoring the missing "!" brings the guest back to life.
> > 
> > Fixes: 00e23707442a ("iov_iter: Use accessor function")
> > Reported-by: Will Deacon <will.deacon@....com>
> > Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> 
> ACK.  Do you want me to take it via vfs.git?  Or might as well
> send directly to Linus, with
> 
> Acked-by Al Viro <viro@...iv.linux.org.uk>
> 
> on it.

Now sent to Linus with your Ack.

Cheers,

	M.

-- 
Jazz is not dead, it just smell funny.