[Qemu-devel] [Bug 1245703] [NEW] LD_PREFIX option reads directories recursively in an endless loop

[Qemu-devel] [Bug 1245703] [NEW] LD_PREFIX option reads directories recursively in an endless loop

[Sebastian Macke]

Public bug reported:

If I run qemu user emulation with -L /path/to/my/sysroot/ in which also
the proc and dev filesystem is mounted QEMU eats my memory until it gets
killed by the kernel.

According to the strace output it follows the symbolic links in the proc
filesystem running forever in a recursive loop.

The easiest solution would be to add in the function "add_dir_maybe" in
the file util/path.c an additional check for symbolic links that it
don't follow them.

Also I don't really understand the need of doing this. A lot of
ressources are wasted everytime QEMU-user is started just by having the
directory structure in memory. In my case this are more than 20000
entries which QEMU is loading every time.

** Affects: qemu
     Importance: Undecided
         Status: New

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Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  New

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
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Re: [Qemu-devel] [Bug 1245703] [NEW] LD_PREFIX option reads directories recursively in an endless loop

[Peter Maydell]

On 28 October 2013 23:15, Sebastian Macke <sebastian@macke.de> wrote:
> If I run qemu user emulation with -L /path/to/my/sysroot/ in which also
> the proc and dev filesystem is mounted QEMU eats my memory until it gets
> killed by the kernel.
>
> According to the strace output it follows the symbolic links in the proc
> filesystem running forever in a recursive loop.
>
> The easiest solution would be to add in the function "add_dir_maybe" in
> the file util/path.c an additional check for symbolic links that it
> don't follow them.

Yeah, this -L code is just busted. It's really only intended to work
with extremely simple sysroot directories which don't have weird
stuff like proc mounts or symlinks and aren't very big.

If the thing you're looking at isn't like that then you might be better
off using the "static qemu and chroot into the directory" approach
instead.

-- PMM

[Qemu-devel] [Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Sebastian Macke]

Ok, thanks for the info.
For me it looks like removing the whole path code and putting a one-liner combining two string is the best solution. But maybe I am missing something.

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Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  New

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1245703/+subscriptions

[Qemu-devel] [Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Antonis Kanouras]

qemu-arm *and* qemu-arm-static 1.5.0+dfsg-3ubuntu5.1 (AMD64 13.10 host)
are affected by this.

Steps to reproduce:
0. mkdir /mnt/mychroot
1. qemu-debootstrap --arch=armhf wheezy /mnt/mychroot http://ftp.debian.org/debian
2. qemu-arm-static -L /mnt/mychroot /mnt/mychroot/usr/sbin/chroot /mnt/mychroot /bin/sh

In this case, the loop starts when it meets /mnt/mychroot/dev/fd (which
links to /proc/self/fd).

** Bug watch added: Debian Bug tracker #636035
   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=636035

** Also affects: qemu (Debian) via
   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=636035
   Importance: Unknown
       Status: Unknown

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Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  New
Status in “qemu” package in Debian:
  Unknown

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
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[Qemu-devel] [Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Antonis Kanouras]

One ugly workaround is, in case anyone needs it:

cp -a /usr/bin/qemu-arm-static /mnt/mychroot/
chroot /mnt/mychroot /qemu-arm-static /bin/sh

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Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  New
Status in “qemu” package in Debian:
  Unknown

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1245703/+subscriptions

[Qemu-devel] [Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Bug Watch Updater]

** Changed in: qemu (Debian)
       Status: Unknown => Confirmed

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https://bugs.launchpad.net/bugs/1245703

Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  New
Status in “qemu” package in Debian:
  Confirmed

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1245703/+subscriptions

[Qemu-devel] [Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Ross Burton]

We're (Yocto Project) hit this often.  We're building a root file system
and then using userspace qemu to run binaries inside it (such as fc-
cache).  If a cyclic symlink appears in the rootfs, it blows up.

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Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  New
Status in qemu package in Debian:
  Confirmed

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1245703/+subscriptions

Re: [Qemu-devel] [Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Peter Maydell]

On 26 March 2015 at 21:37, Ross Burton <ross@burtonini.com> wrote:
> We're (Yocto Project) hit this often.  We're building a root file system
> and then using userspace qemu to run binaries inside it (such as fc-
> cache).  If a cyclic symlink appears in the rootfs, it blows up.

If you're actually building a rootfs then you're probably
better off using binfmt-misc and chrooting into it rather
than using -L. -L really isn't intended to point at a
full rootfs.

-- PMM

[Qemu-devel] [Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Ross Burton]

We need to be able to run qemu as not root.  Has anyone tried using qemu
with fakechroot?

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Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  New
Status in qemu package in Debian:
  Confirmed

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1245703/+subscriptions

[Qemu-devel] [Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Peter Maydell]

** Changed in: qemu
       Status: New => Confirmed

** Tags added: linux-user

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Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  Confirmed
Status in qemu package in Debian:
  Confirmed

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1245703/+subscriptions

[Qemu-devel] [Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Richard Henderson]

I posted a patch a while back that would fix this:

https://patchwork.kernel.org/patch/9512083/

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Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  Confirmed
Status in qemu package in Debian:
  Confirmed

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1245703/+subscriptions

[Qemu-devel] [Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Bug Watch Updater]

** Changed in: qemu (Debian)
       Status: Confirmed => Fix Released

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https://bugs.launchpad.net/bugs/1245703

Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  Confirmed
Status in qemu package in Debian:
  Fix Released

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1245703/+subscriptions

[Bug 1245703] Re: LD_PREFIX option reads directories recursively in an endless loop

[Laurent Vivier]

Fixed by in 4.1.0 by:

f3a8bdc1d5b2 ("util/path: Do not cache all filenames at startup")


** Changed in: qemu
       Status: Confirmed => Fix Released

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Title:
  LD_PREFIX option reads directories recursively in an endless loop

Status in QEMU:
  Fix Released
Status in qemu package in Debian:
  Fix Released

Bug description:
  If I run qemu user emulation with -L /path/to/my/sysroot/ in which
  also the proc and dev filesystem is mounted QEMU eats my memory until
  it gets killed by the kernel.

  According to the strace output it follows the symbolic links in the
  proc filesystem running forever in a recursive loop.

  The easiest solution would be to add in the function "add_dir_maybe"
  in the file util/path.c an additional check for symbolic links that it
  don't follow them.

  Also I don't really understand the need of doing this. A lot of
  ressources are wasted everytime QEMU-user is started just by having
  the directory structure in memory. In my case this are more than 20000
  entries which QEMU is loading every time.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1245703/+subscriptions