blkid: exit code as non-root user, and segfault

blkid: exit code as non-root user, and segfault

[Bernhard Voelker]

blkid returns 0 without output when running as non-root user
and when the cache /dev/.blkid.tab is not yet there:

  ./blkid /dev/sdb3 ; echo $?
  0

That's the strace:

  open("/dev/.blkid.tab", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
  access("/dev/sdb3", F_OK)               = 0
  stat("/dev/sdb3", {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 19), ...}) = 0
  open("/dev/sdb3", O_RDONLY|O_CLOEXEC)   = -1 EACCES (Permission denied)
  stat("/dev/.blkid.tab", 0x7fff2b7cc990) = -1 ENOENT (No such file or directory)
  open("/dev/.blkid.tab", O_WRONLY|O_CREAT|O_TRUNC, 0666) = -1 EACCES (Permission denied)
  close(1)                                = 0
  close(2)                                = 0
  exit_group(0)                           = ?

I'd have expected either an error message along with exit code 1,
or success with some useful output.

After the cache exists, it's fine:

  ./blkid  /dev/sdb3 ; echo $?
  /dev/sdb3: LABEL="home" UUID="41ec7daa-46c3-4f19-aea0-e2c1679bb557" TYPE="ext3"
  0


And another issue: blkid segfaults with this - okay, bad use of options:

  ./blkid -n /dev/sdb3
  Segmentation fault

Backtrace:
  (gdb) bt
  #0  0x00007ff64fe72121 in __strlen_sse2 () from /lib64/libc.so.6
  #1  0x00007ff65039029b in blkid_dev_set_search (iter=0x6090c0, search_type=0x0, search_value=0x0) at
libblkid/src/dev.c:151
  #2  0x00000000004036e8 in main (argc=<optimized out>, argv=<optimized out>) at misc-utils/blkid.c:925

Using latest git; it doesn't dump core with 2.20.1.

Have a nice day,
Berny

Re: blkid: exit code as non-root user, and segfault

[Karel Zak]

On Sun, Dec 09, 2012 at 06:52:29PM +0100, Bernhard Voelker wrote:
> blkid returns 0 without output when running as non-root user
> and when the cache /dev/.blkid.tab is not yet there:
> 
>   ./blkid /dev/sdb3 ; echo $?
>   0

./blkid /dev/sdb3; echo $?2
2

> And another issue: blkid segfaults with this - okay, bad use of options:
> 
>   ./blkid -n /dev/sdb3
>   Segmentation fault

 Fixed by:

 commit 2e31fe2303e4938ef735aebf13aa5b22fb031af9
 Author: Karel Zak <kzak@redhat.com>
 Date:   Tue Dec 4 11:58:13 2012 +0100

     libblkid: cleanup nonnull attribute usage


> Using latest git; it doesn't dump core with 2.20.1.

 Really latest? ;-)

    Karel


-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

Re: blkid: exit code as non-root user, and segfault

[Bernhard Voelker]

On December 10, 2012 at 9:42 AM Karel Zak <kzak@redhat.com> wrote:
> On Sun, Dec 09, 2012 at 06:52:29PM +0100, Bernhard Voelker wrote:
> > blkid returns 0 without output when running as non-root user
> > and when the cache /dev/.blkid.tab is not yet there:
> >
> >   ./blkid /dev/sdb3 ; echo $?
> >   0
>
> ./blkid /dev/sdb3; echo $?2
> 2

Typo? "$?2" should lead to "02".

It really exits 0 here, when run as non-root user and when
/dev/.blkid.tab doesn't exist yet.

> > And another issue: blkid segfaults with this - okay, bad use of options:
> >
> >   ./blkid -n /dev/sdb3
> >   Segmentation fault
>
>  Fixed by:
...
> > Using latest git; it doesn't dump core with 2.20.1.
>
>  Really latest? ;-)

Yes, now (forgot make after pull, sorry) ;-)

Ok, that means the segfault is fixed, but the above
issue is still there.

Have a nice day,
Berny

Re: blkid: exit code as non-root user, and segfault

[Karel Zak]

On Mon, Dec 10, 2012 at 09:58:34AM +0100, Bernhard Voelker wrote:
> 
> On December 10, 2012 at 9:42 AM Karel Zak <kzak@redhat.com> wrote:
> > On Sun, Dec 09, 2012 at 06:52:29PM +0100, Bernhard Voelker wrote:
> > > blkid returns 0 without output when running as non-root user
> > > and when the cache /dev/.blkid.tab is not yet there:
> > >
> > >   ./blkid /dev/sdb3 ; echo $?
> > >   0
> >
> > ./blkid /dev/sdb3; echo $?2
> > 2
> 
> Typo? "$?2" should lead to "02".

 copy & past bug

> It really exits 0 here, when run as non-root user and when
> /dev/.blkid.tab doesn't exist yet.

Anyway, I have tested the problem as root. You're right it is
possible to reproduce as non-root. Sorry.

I'll fix it. Thanks.

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

Re: blkid: exit code as non-root user, and segfault

[Karel Zak]

On Sun, Dec 09, 2012 at 06:52:29PM +0100, Bernhard Voelker wrote:
> blkid returns 0 without output when running as non-root user
> and when the cache /dev/.blkid.tab is not yet there:
> 
>   ./blkid /dev/sdb3 ; echo $?
>   0

 [...]

>   access("/dev/sdb3", F_OK)               = 0
>   stat("/dev/sdb3", {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 19), ...}) = 0

 [...]

> I'd have expected either an error message along with exit code 1,
> or success with some useful output.

 Well, it seems that the code differentiate between:

  a) device does not exist:

      $ blkid /dev/FooBar; echo $?
      2

     or exists but does not match:

      $ blkid -t LABEL=xyz /dev/sda1; echo $?
      2

  b) device exists, but there is nothing to print

      $ blkid /dev/sda1; echo $?
      0

     just for the record, you can always print device name:

      $ blkid -o device /dev/sda1; echo $?
      /dev/sda1
      0


 maybe it's not obvious at a first glance, but the current behavior
 seems correct.

 Maybe we can detect the special situation (and print a warning
 message) when the cache is empty and user is non-root to make it more
 user-friendly. I'm not sure if any change in return code is necessary.

    Karel


-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com