[Bug dynamic-link/17353] New: ldd no longer works with non-executable .so files

[Bug dynamic-link/17353] New: ldd no longer works with non-executable .so files

[brooks at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=17353

            Bug ID: 17353
           Summary: ldd no longer works with non-executable .so files
           Product: glibc
           Version: 2.18
            Status: NEW
          Severity: normal
          Priority: P2
         Component: dynamic-link
          Assignee: unassigned at sourceware dot org
          Reporter: brooks at gcc dot gnu.org

I am not sure if this is a glibc regression from 2.15 to 2.18, or a glibc vs.
eglibc difference, since my two points of comparison are system tools on Ubuntu
12.04 and 14.04.  With that said, consider this .so file that doesn't have the
executable bit set:

$ ls python2.7/lib-dynload/pyexpat.so -l
-rw-r--r-- 1 root root 286314 Jul 11 12:12 python2.7/lib-dynload/pyexpat.so

$ ${eglibc215}/bin/ldd python2.7/lib-dynload/pyexpat.so
        linux-vdso.so.1 =>  (0x00007fff1e3b7000)
[and so on]

$ ${glibc218}/bin/ldd python2.7/lib-dynload/pyexpat.so
ldd: warning: you do not have execution permission for
`python2.7/lib-dynload/pyexpat.so'
ldd: line 117: python2.7/lib-dynload/pyexpat.so: Permission denied

The warning seems reasonable, but failing to track down the linkages for the
library because of the missing executable bit seems like an unnecessary error,
since (a) it used to work, and (b) the library is otherwise entirely functional
without the execute bit set.

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[Bug dynamic-link/17353] ldd no longer works with non-executable .so files

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17353

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING
                 CC|                            |fweimer at redhat dot com
              Flags|                            |security-

--- Comment #1 from Florian Weimer <fweimer at redhat dot com> ---
This might be an Ubuntu-specific change, perhaps related to making it harder to
execute non-executable files using ld.so.  I cannot reproduce this with several
post-2.18 glibc versions.

Could you check the Ubuntu documentation and see if they have changed anything
in this area?

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[Bug dynamic-link/17353] ldd no longer works with non-executable .so files

[brooks at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=17353

--- Comment #2 from Brooks Moses <brooks at gcc dot gnu.org> ---
Created attachment 7778
  --> https://sourceware.org/bugzilla/attachment.cgi?id=7778&action=edit
Patch from Ubuntu 2.19 sources.

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[Bug dynamic-link/17353] ldd no longer works with non-executable .so files

[brooks at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=17353

Brooks Moses <brooks at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |UNCONFIRMED
     Ever confirmed|1                           |0

--- Comment #3 from Brooks Moses <brooks at gcc dot gnu.org> ---
Sorry, Florian, I was typing this up at the end of the long day and made a
couple of errors.  First, where I said 2.18, I meant 2.19.  Second, I should
have clarified that although I'm using versions that match the Ubuntu system
tools, the 2.19 ldd that I was using was built from upstream glibc source.

In particular, I think the difference is due to the patch I just attached,
which came from the Ubuntu source package.  If I apply the inverse of this
patch to the Ubuntu 14.04 system ldd, I get the "Permission denied" error.

Likewise, if I apply this patch to the ldd built from upstream 2.19, it now
works correctly with non-executable .so files.

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[Bug dynamic-link/17353] ldd no longer works with non-executable .so files

[brooks at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=17353

--- Comment #4 from Brooks Moses <brooks at gcc dot gnu.org> ---
And I still seem to be being not entirely clear.  So, let me try again: I'm
seeing the following behaviors:

* ldd shipped with Ubuntu 12.04 (from patched eglibc 2.15): Works fine with
non-executable libraries.
* ldd shipped with Ubuntu 14.04 (from patched eglibc 2.19): Works fine with
non-executable libraries.
* ldd from the glibc 2.19 I built from upstream sources: Does not work with
non-executable libraries.

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