TMPFS permissions bug in 2.6.35-rc3

TMPFS permissions bug in 2.6.35-rc3

[Chuck Fox]

Hugh & List:

   I've encountered a bug in 2.6.35-RC3 where my /tmp directory
(mounted using tmpfs) returns a "File too large" error when adding
execute privileges for the group permission byte:
       Example:
           touch /tmp/afile
           chmod 767 /tmp/afile   # example where chmod works fine
setting bits that are not the group execute bit
           chmod 755 /tmp/afile
           chmod: changing permissions of `/tmp/afile': File too large  # bug

   There are several gigabytes of free RAM + several more gigabytes of
swap space available.

   Here's more information:

   scripts/ver_linux

If some fields are empty or look unusual you may have an old version.
Compare to the current minimal requirements in Documentation/Changes.

Linux alpha1 2.6.35-rc3-next-20100614 #5 SMP Sun Jun 20 18:55:35 EDT
2010 x86_64 Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz GenuineIntel
GNU/Linux

Gnu C                  4.5.0
Gnu make               3.81
binutils               2.20.1.20100521
util-linux             2.17.2
mount                  support
module-init-tools      3.11.1
e2fsprogs              1.41.12
Linux C Library        2.12
Dynamic linker (ldd)   2.12
Linux C++ Library      6.0.14
Procps                 3.2.8
Net-tools              1.60
Kbd                    1.15.2
Sh-utils               8.5
Modules Loaded         w83627ehf hwmon_vid coretemp
snd_hda_codec_analog nvidia snd_seq_dummy snd_seq_oss
snd_seq_midi_event snd_seq snd_seq_device tun snd_pcm_oss
snd_mixer_oss i2c_i801 sg snd_hda_intel snd_hda_codec snd_pcm
snd_page_alloc e1000e sky2


My fstab entries for mounting /dev/shm and for /tmp:

tmpfs                   /dev/shm      tmpfs     defaults            0      0
tmpfs /tmp tmpfs defaults,noatime,nosuid,mode=1777 0 0


Let me know if there is anything else I can provide to help hunt down the bug!

P.S. --> I got your email from a list of kernel maintainers, if there
is another address this report should go to, please let me know & I'll
forward it.

-- 
Chuck Fox

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Re: TMPFS permissions bug in 2.6.35-rc3

[Chuck Fox]

Some more information on the bug:

   1. If the superuser is the owner of the file in the tmpfs
filesystem, then the chmod command will work appropriately for the
superuser.
         a. this applies even if I change the group of the file to the
same group as a regular user, the bug does not appear as long as the
owner is 'root'
   2. If the superuser is not the owner of the file, then the bug
appears even if the superuser invokes chmod on the file.
   3. I originally had the posix_acl support for tmpfs turned on, but
I reconfigured the kernel with it turned off.. the bug was unaffected.


On Sun, Jun 20, 2010 at 8:52 PM, Chuck Fox <cfox04@gmail.com> wrote:
> Hugh & List:
>
>   I've encountered a bug in 2.6.35-RC3 where my /tmp directory
> (mounted using tmpfs) returns a "File too large" error when adding
> execute privileges for the group permission byte:
>       Example:
>           touch /tmp/afile
>           chmod 767 /tmp/afile   # example where chmod works fine
> setting bits that are not the group execute bit
>           chmod 755 /tmp/afile
>           chmod: changing permissions of `/tmp/afile': File too large  # bug
>
>   There are several gigabytes of free RAM + several more gigabytes of
> swap space available.
>
>   Here's more information:
>
>   scripts/ver_linux
>
> If some fields are empty or look unusual you may have an old version.
> Compare to the current minimal requirements in Documentation/Changes.
>
> Linux alpha1 2.6.35-rc3-next-20100614 #5 SMP Sun Jun 20 18:55:35 EDT
> 2010 x86_64 Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz GenuineIntel
> GNU/Linux
>
> Gnu C                  4.5.0
> Gnu make               3.81
> binutils               2.20.1.20100521
> util-linux             2.17.2
> mount                  support
> module-init-tools      3.11.1
> e2fsprogs              1.41.12
> Linux C Library        2.12
> Dynamic linker (ldd)   2.12
> Linux C++ Library      6.0.14
> Procps                 3.2.8
> Net-tools              1.60
> Kbd                    1.15.2
> Sh-utils               8.5
> Modules Loaded         w83627ehf hwmon_vid coretemp
> snd_hda_codec_analog nvidia snd_seq_dummy snd_seq_oss
> snd_seq_midi_event snd_seq snd_seq_device tun snd_pcm_oss
> snd_mixer_oss i2c_i801 sg snd_hda_intel snd_hda_codec snd_pcm
> snd_page_alloc e1000e sky2
>
>
> My fstab entries for mounting /dev/shm and for /tmp:
>
> tmpfs                   /dev/shm      tmpfs     defaults            0      0
> tmpfs /tmp tmpfs defaults,noatime,nosuid,mode=1777 0 0
>
>
> Let me know if there is anything else I can provide to help hunt down the bug!
>
> P.S. --> I got your email from a list of kernel maintainers, if there
> is another address this report should go to, please let me know & I'll
> forward it.
>
> --
> Chuck Fox
>



-- 
Chuck Fox

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
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Re: TMPFS permissions bug in 2.6.35-rc3

[Hugh Dickins]

On Sun, 20 Jun 2010, Chuck Fox wrote:
> 
>    I've encountered a bug in 2.6.35-RC3 where my /tmp directory
> (mounted using tmpfs) returns a "File too large" error when adding
> execute privileges for the group permission byte:
>        Example:
>            touch /tmp/afile
>            chmod 767 /tmp/afile   # example where chmod works fine
> setting bits that are not the group execute bit
>            chmod 755 /tmp/afile
>            chmod: changing permissions of `/tmp/afile': File too large  # bug

How very peculiar!  Thank you for reporting it.  I was about to suggest
some memory corruption must have occurred, but no....

> 
>    There are several gigabytes of free RAM + several more gigabytes of
> swap space available.
> 
>    Here's more information:
> 
> Linux alpha1 2.6.35-rc3-next-20100614 #5 SMP Sun Jun 20 18:55:35 EDT
> 2010 x86_64 Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz GenuineIntel
> GNU/Linux
> ...

... that's actually one of the linux-next kernels you're running there:
and I bet you'll find Jiri's patch below fixes your problem!