Linux-Fsdevel Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Al Viro <viro@zeniv.linux.org.uk>
To: Thiago Macieira <thiago.macieira@intel.com>
Cc: linux-fsdevel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: fcntl(F_DUPFD) causing apparent file descriptor table corruption
Date: Tue, 19 May 2020 23:28:32 +0100	[thread overview]
Message-ID: <20200519222832.GU23230@ZenIV.linux.org.uk> (raw)
In-Reply-To: <6266026.WxYS4g2YVZ@tjmaciei-mobl1>

On Tue, May 19, 2020 at 03:18:13PM -0700, Thiago Macieira wrote:

> > I really wonder about the missing couple of syscalls in your strace, though;
> > could you verify that they _are_ missing and see what the fix above does to
> > your testcase?
> 
> Looking at my terminal backtrace, I might have made a copy & paste mistake of 
> the trace while flipping pages. Unfortunately, the trace file I had in /tmp 
> was lost because I needed to reboot the machine. The other traces I have in my 
> terminal show:
> 
> fcntl(2, F_DUPFD, 134217728)            = 134217728
> close(134217728)                        = 0
> fcntl(2, F_DUPFD, 268435456)            = 268435456
> close(268435456)                        = 0
> fcntl(2, F_DUPFD, 536870912)            = 536870912
> close(536870912)                        = 0
> write(1, "success\n", 8)                = ?
> ^C^Czsh: killed     sudo strace ./dupfd-bug
> 
> I had to killall -9 strace at this point. See the attached oops.

BS values in the array of struct file pointers due to the problem above.
And very likely a memory corruption as well.

> Then I insisted:
> 
> fcntl(2, F_DUPFD, 67108864)             = 67108864
> close(67108864)                         = 0
> fcntl(2, F_DUPFD, 134217728)            = 134217728
> close(134217728)                        = 0
> fcntl(2, F_DUPFD, 268435456Shared connection to <REDACTED> closed.
> 
> At this point, I need to drive to the office to reboot the machine. Building 
> the kernel and testing will take a few days.
> 
> Note to self: don't play with possible kernel bugs without a VM.

... at least not without remote console, complete with ability to
powercycle the box.

      reply	other threads:[~2020-05-19 22:28 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19 21:03 Thiago Macieira
2020-05-19 21:45 ` Al Viro
2020-05-19 22:04   ` Al Viro
2020-05-19 22:18   ` Thiago Macieira
2020-05-19 22:28     ` Al Viro [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200519222832.GU23230@ZenIV.linux.org.uk \
    --to=viro@zeniv.linux.org.uk \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=thiago.macieira@intel.com \
    --cc=torvalds@linux-foundation.org \
    --subject='Re: fcntl(F_DUPFD) causing apparent file descriptor table corruption' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).