Re: [PATCH] elf: Use _dl_catch_error from base namespace in dl-libc.c [BZ #27646]

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 6/14/21 3:15 PM, Florian Weimer via Libc-alpha wrote:
> dlerrror_run in elf/dl-libc.c needs to call GLRO (dl_catch_error)
> from the base namespace, just like the exported dlerror
> implementation.
> 
> Fixes commit b2964eb1d9a6b8ab1250e8a881cf406182da5875 ("dlfcn:
> Failures after dlmopen should not terminate process [BZ #24772]").
> 
> Tested on i686-linux-gnu and x86_64-linux-gnu.

LGTM.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

> ---
>   elf/Makefile                        |  5 ++++-
>   elf/dl-libc.c                       |  4 ++--
>   elf/tst-dlmopen-gethostbyname-mod.c | 29 +++++++++++++++++++++++++++++
>   elf/tst-dlmopen-gethostbyname.c     | 31 +++++++++++++++++++++++++++++++
>   4 files changed, 66 insertions(+), 3 deletions(-)
> 
> diff --git a/elf/Makefile b/elf/Makefile
> index 5c47daee12..38d08e03b8 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -223,7 +223,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
>   	 tst-single_threaded tst-single_threaded-pthread \
>   	 tst-tls-ie tst-tls-ie-dlmopen argv0test \
>   	 tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
> -	 tst-tls20 tst-tls21 tst-dlmopen-dlerror
> +	 tst-tls20 tst-tls21 tst-dlmopen-dlerror tst-dlmopen-gethostbyname
>   #	 reldep9
>   tests-internal += loadtest unload unload2 circleload1 \
>   	 neededtest neededtest2 neededtest3 neededtest4 \
> @@ -347,6 +347,7 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
>   		libmarkermod4-1 libmarkermod4-2 libmarkermod4-3 libmarkermod4-4 \
>   		tst-tls20mod-bad tst-tls21mod tst-dlmopen-dlerror-mod \
>   		tst-auxvalmod \
> +		tst-dlmopen-gethostbyname-mod \
>   
>   # Most modules build with _ISOMAC defined, but those filtered out
>   # depend on internal headers.
> @@ -1832,3 +1833,5 @@ $(objpfx)tst-tls21mod.so: $(tst-tls-many-dynamic-modules:%=$(objpfx)%.so)
>   
>   $(objpfx)tst-getauxval-static.out: $(objpfx)tst-auxvalmod.so
>   tst-getauxval-static-ENV = LD_LIBRARY_PATH=$(objpfx):$(common-objpfx)
> +
> +$(objpfx)tst-dlmopen-gethostbyname.out: $(objpfx)tst-dlmopen-gethostbyname-mod.so
> diff --git a/elf/dl-libc.c b/elf/dl-libc.c
> index 8e0734f44c..a49df22029 100644
> --- a/elf/dl-libc.c
> +++ b/elf/dl-libc.c
> @@ -43,8 +43,8 @@ dlerror_run (void (*operate) (void *), void *args)
>     const char *last_errstring = NULL;
>     bool malloced;
>   
> -  int result = (_dl_catch_error (&objname, &last_errstring, &malloced,
> -				operate, args)
> +  int result = (GLRO (dl_catch_error) (&objname, &last_errstring, &malloced,
> +				       operate, args)
>   		?: last_errstring != NULL);
>   
>     if (result && malloced)
> diff --git a/elf/tst-dlmopen-gethostbyname-mod.c b/elf/tst-dlmopen-gethostbyname-mod.c
> new file mode 100644
> index 0000000000..9a68ea5050
> --- /dev/null
> +++ b/elf/tst-dlmopen-gethostbyname-mod.c
> @@ -0,0 +1,29 @@
> +/* Exercise dlerror_run in elf/dl-libc.c after dlmopen, via NSS.  Helper module.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <netdb.h>
> +#include <nss.h>
> +
> +void
> +call_gethostbyname (void)
> +{
> +  __nss_configure_lookup ("hosts", "files");
> +  /* This should not terminate the process due to a missing
> +     _nss_files_getcanonname_r symbol.  */
> +  gethostbyname ("localhost");
> +}
> diff --git a/elf/tst-dlmopen-gethostbyname.c b/elf/tst-dlmopen-gethostbyname.c
> new file mode 100644
> index 0000000000..12deb29900
> --- /dev/null
> +++ b/elf/tst-dlmopen-gethostbyname.c
> @@ -0,0 +1,31 @@
> +/* Exercise dlerror_run in elf/dl-libc.c after dlmopen, via NSS (bug 27646).
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <support/xdlfcn.h>
> +
> +static int
> +do_test (void)
> +{
> +  void *handle = xdlmopen (LM_ID_NEWLM, "tst-dlmopen-gethostbyname-mod.so",
> +                           RTLD_NOW);
> +  void (*call_gethostbyname) (void) = xdlsym (handle, "call_gethostbyname");
> +  call_gethostbyname ();
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
>