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Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c

From Al Viro <viro@ZenIV.linux.org.uk>
Newsgroups linux.kernel
Subject Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c
Date 2016-05-25 03:30 +0200
Message-ID <rCvO2-2Kd-17@gated-at.bofh.it> (permalink)
References (5 earlier) <rCt9w-R2-37@gated-at.bofh.it> <rCuff-1yS-3@gated-at.bofh.it> <rCvkZ-2kP-3@gated-at.bofh.it> <rCvEl-2H1-1@gated-at.bofh.it> <rCvO2-2Kd-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Tue, May 24, 2016 at 08:20:46PM -0500, Matthew McClintock wrote:
> 
> > On May 24, 2016, at 8:10 PM, Al Viro <viro@ZenIV.linux.org.uk> wrote:
> > 
> > Slap the WARN_ON(!size); in the very beginning of iov_iter_advance(), see
> > where it's triggered...
> 
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 28cb431..d89e154 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -488,6 +488,7 @@ EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
> 
>  void iov_iter_advance(struct iov_iter *i, size_t size)
>  {
> +       WARN_ON(!size);
>         iterate_and_advance(i, size, v, 0, 0, 0)
>  }
>  EXPORT_SYMBOL(iov_iter_advance);
> 
> [    1.359869] This architecture does not have kernel memory protection.
> init started: BusyBox v1.24.1 ()
> starting pid 78, tty '': '/etc/init.d/rcS'
> [    1.435863] random: udevadm urandom read with 0 bits of entropy available
> [    1.448116] ------------[ cut here ]------------
> [    1.448193] WARNING: CPU: 1 PID: 88 at lib/iov_iter.c:491 iov_iter_advance+0xf0/0x1b8

The next obvious question is which binary it is and what's the return
address to userland; make that
	if (!size)
		printk(KERN_ERR "crap in %s[%x]",
			current->comm,
			current_pt_regs()->rip);
(in the same place)

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Thread

Regression in 4.6.0-git - bisected to commit dd254f5a382c Larry Finger <Larry.Finger@lwfinger.net> - 2016-05-23 23:40 +0200
  Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Al Viro <viro@ZenIV.linux.org.uk> - 2016-05-24 02:20 +0200
    Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Larry Finger <Larry.Finger@lwfinger.net> - 2016-05-24 05:00 +0200
    Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Larry Finger <Larry.Finger@lwfinger.net> - 2016-05-24 18:20 +0200
      Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Al Viro <viro@ZenIV.linux.org.uk> - 2016-05-24 18:30 +0200
        Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Larry Finger <Larry.Finger@lwfinger.net> - 2016-05-24 20:40 +0200
      Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Matthew McClintock <mmcclint@codeaurora.org> - 2016-05-24 21:20 +0200
        Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Larry Finger <Larry.Finger@lwfinger.net> - 2016-05-24 21:20 +0200
          Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Matthew McClintock <mmcclint@codeaurora.org> - 2016-05-24 21:30 +0200
            Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Larry Finger <Larry.Finger@lwfinger.net> - 2016-05-24 21:40 +0200
              Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Matthew McClintock <mmcclint@codeaurora.org> - 2016-05-25 00:40 +0200
                Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Al Viro <viro@ZenIV.linux.org.uk> - 2016-05-25 01:50 +0200
                Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Matthew McClintock <mmcclint@codeaurora.org> - 2016-05-25 03:00 +0200
                Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Al Viro <viro@ZenIV.linux.org.uk> - 2016-05-25 03:20 +0200
                Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Matthew McClintock <mmcclint@codeaurora.org> - 2016-05-25 03:30 +0200
                Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Al Viro <viro@ZenIV.linux.org.uk> - 2016-05-25 03:30 +0200
                Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Matthew McClintock <mmcclint@codeaurora.org> - 2016-05-25 04:10 +0200
                Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Al Viro <viro@ZenIV.linux.org.uk> - 2016-05-25 05:30 +0200
                Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Al Viro <viro@ZenIV.linux.org.uk> - 2016-05-25 08:30 +0200
                Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Larry Finger <Larry.Finger@lwfinger.net> - 2016-05-25 16:30 +0200
                Re: Regression in 4.6.0-git - bisected to commit dd254f5a382c Matthew McClintock <mmcclint@codeaurora.org> - 2016-05-25 17:30 +0200

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