[Bug runtime/31373] New: Allow systemtap to work on kernels without strlcpy (removed in the linux-6.8.0-rc3 kernels)

[Bug runtime/31373] New: Allow systemtap to work on kernels without strlcpy (removed in the linux-6.8.0-rc3 kernels)

[wcohen at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31373

            Bug ID: 31373
           Summary: Allow systemtap to work on kernels without strlcpy
                    (removed in the linux-6.8.0-rc3 kernels)
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
          Assignee: systemtap at sourceware dot org
          Reporter: wcohen at redhat dot com
  Target Milestone: ---

The latest linux kernels have removed strlcpy with kernel git commit
d26270061ae66b915138af7cd73ca6f8b85e6b44 :

Author: Kees Cook <keescook@chromium.org>  2024-01-18 15:31:55
Committer: Kees Cook <keescook@chromium.org>  2024-01-19 14:59:11
Parent: e28b0359587fe4055c838698172de0530b511702 (bcachefs: Replace strlcpy()
with strscpy())
Child:  57f22c8dab6b266ae36b89b073a4a33dea71e762 (Merge tag
'strlcpy-removal-v6.8-rc1' of
git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux)
Branches: master, remotes/origin/master
Follows: v6.7
Precedes: v6.8-rc1

    string: Remove strlcpy()

    With all the users of strlcpy() removed[1] from the kernel, remove the
    API, self-tests, and other references. Leave mentions in Documentation
    (about its deprecation), and in checkpatch.pl (to help migrate host-only
    tools/ usage). Long live strscpy().

    Link: https://github.com/KSPP/linux/issues/89 [1]
    Cc: Azeem Shaikh <azeemshaikh38@gmail.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Andy Whitcroft <apw@canonical.com>
    Cc: Joe Perches <joe@perches.com>
    Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
    Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
    Cc: linux-hardening@vger.kernel.org
    Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
    Signed-off-by: Kees Cook <keescook@chromium.org>


Without the strlcpy function in the kernel systemtap scripts fail to build as
seen below:

$ ../install/bin/stap -p4 testsuite/systemtap.examples/general/ansi_colors.stp
In file included from
/home/wcohen/systemtap_write/install/share/systemtap/runtime/linux/runtime.h:325,
                 from
/home/wcohen/systemtap_write/install/share/systemtap/runtime/runtime.h:26,
                 from
/tmp/stapBVBodh/stap_a3ae1fd74dcbac47ca75cf2713720668_2212_src.c:21:
/home/wcohen/systemtap_write/install/share/systemtap/runtime/stp_string.c: In
function ‘_stp_text_str’:
/home/wcohen/systemtap_write/install/share/systemtap/runtime/stp_string.c:304:9:
error: implicit declaration of function ‘strlcpy’; did you mean ‘strscpy’?
[-Wimplicit-function-declaration]
  304 |         strlcpy (outstr, "<unknown>", outlen);
      |         ^~~~~~~
      |         strscpy
make[1]: *** [scripts/Makefile.build:243:
/tmp/stapBVBodh/stap_a3ae1fd74dcbac47ca75cf2713720668_2212_src.o] Error 1
make: *** [Makefile:1939: /tmp/stapBVBodh] Error 2
WARNING: kbuild exited with status: 2
Pass 4: compilation failed.  [man error::pass4]
Kernel version 6.8.0 is outside tested range 2.6.32 ... 6.8-rc0

See a number of strlcpy in runtime directory, but there are also strscpy calls
in the tapset directory and some of the *.cxx files.  There is some discussion
about the move from strlcpy to strscpy in https://lwn.net/Articles/659214/ .  
One thing to note is that strlcpy and strscpy have different return value
semantics and there are some places where the return value of strlcpy is being
used.

The strscpy function was added to the linux kernel with git commit
30035e45753b708e7d47a98398500ca005e02b86 around 2015-04-29 and is available in
Linux 4.3 and newer kernels.

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[Bug runtime/31373] Allow systemtap to work on kernels without strlcpy (removed in the linux-6.8.0-rc3 kernels)

[fche at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31373

Frank Ch. Eigler <fche at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fche at redhat dot com

--- Comment #1 from Frank Ch. Eigler <fche at redhat dot com> ---
In our case, with trusted inputs / lengths, it may be enough to

#define strlcpy strscpy

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[Bug runtime/31373] Allow systemtap to work on kernels without strlcpy (removed in the linux-6.8.0-rc3 kernels)

[wcohen at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31373

--- Comment #2 from William Cohen <wcohen at redhat dot com> ---
Created attachment 15361
  --> https://sourceware.org/bugzilla/attachment.cgi?id=15361&action=edit
Proposed define to map the strlcpy to strscpy

The suggestion was the approach that this patch is taking. However, there are
some places in the generated code that make use of the return value to track
the amount of buffer space used by the operation. The proposed patch adjusts
the strscpy return value to make it compatible with the existing uses of the
strlcpy return value.

The macro definition need to be placed where it is only used by the systemtap
generated module.  Currently it pulled into code for code for the dyninst
target and causes the dyninst target code to not compile..

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[Bug runtime/31373] Allow systemtap to work on kernels without strlcpy (removed in the linux-6.8.0-rc3 kernels)

[wcohen at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31373

--- Comment #3 from William Cohen <wcohen at redhat dot com> ---
Created attachment 15362
  --> https://sourceware.org/bugzilla/attachment.cgi?id=15362&action=edit
Revised patch with macro where only systemtap kernel modules use it.

Looked around runtime code.  Found a place in runtime/linux where
<linux/string.h> is included and placed the macro after that to ensure had the
strscpy declaration.  Tried the patch out and systemtap dyninst backend tests
are working.

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[Bug runtime/31373] Allow systemtap to work on kernels without strlcpy (removed in the linux-6.8.0-rc3 kernels)

[wcohen at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31373

William Cohen <wcohen at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #4 from William Cohen <wcohen at redhat dot com> ---
This has been addressed by git commit 60c3d8b1c90c58ca7c048ef24e1b03c6c04b36ad.

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