diff mbox series

[1/5] elf: Fix audit regression

Message ID 20210707182610.3940620-2-adhemerval.zanella@linaro.org
State Superseded
Headers
Series Some rtld-audit fixes |

Checks

Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent

Commit Message

Adhemerval Zanella Netto July 7, 2021, 6:26 p.m. UTC 
  Commit 03e187a41d9 added a regression when an audit module does not have
libc as DT_NEEDED (although unusual it is possible).

Checked on x86_64-linux-gnu.
---
 elf/Makefile         | 12 +++++++++++-
 elf/dl-open.c        |  2 +-
 elf/tst-audit17.c    | 25 +++++++++++++++++++++++++
 elf/tst-auditmod17.c | 24 ++++++++++++++++++++++++
 4 files changed, 61 insertions(+), 2 deletions(-)
 create mode 100644 elf/tst-audit17.c
 create mode 100644 elf/tst-auditmod17.c

Comments

Florian Weimer July 7, 2021, 7:02 p.m. UTC | #1 
* Adhemerval Zanella via Libc-alpha:

> diff --git a/elf/Makefile b/elf/Makefile
> index b1e01d9516..5214196de6 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile

> @@ -361,6 +361,7 @@ modules-names += tst-gnu2-tls1mod
>  $(objpfx)tst-gnu2-tls1: $(objpfx)tst-gnu2-tls1mod.so
>  tst-gnu2-tls1mod.so-no-z-defs = yes
>  CFLAGS-tst-gnu2-tls1mod.c += -mtls-dialect=gnu2
> +

Spurious whitespace change.  Or rather, missing CFLAGS for
tst-auditmod17 to disable stack protector.  I expect the test to fail
when building glibc with -fstack-protector-all.

> diff --git a/elf/dl-open.c b/elf/dl-open.c
> index a066f39bd0..66ec9d7ed5 100644
> --- a/elf/dl-open.c
> +++ b/elf/dl-open.c
> @@ -771,7 +771,7 @@ dl_open_worker (void *a)
>      {
>        struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
>  #ifdef SHARED
> -      bool initial = libc_map->l_ns == LM_ID_BASE;
> +      bool initial = libc_map != NULL ? libc_map->l_ns == LM_ID_BASE : false;
>  #else
>        /* In the static case, there is only one namespace, but it
>  	 contains a secondary libc (the primary libc is statically

Looks okay to me.  The previous code was just broken.

Thanks,
Florian
Adhemerval Zanella Netto July 7, 2021, 7:07 p.m. UTC | #2 
On 07/07/2021 16:02, Florian Weimer wrote:
> * Adhemerval Zanella via Libc-alpha:
> 
>> diff --git a/elf/Makefile b/elf/Makefile
>> index b1e01d9516..5214196de6 100644
>> --- a/elf/Makefile
>> +++ b/elf/Makefile
> 
>> @@ -361,6 +361,7 @@ modules-names += tst-gnu2-tls1mod
>>  $(objpfx)tst-gnu2-tls1: $(objpfx)tst-gnu2-tls1mod.so
>>  tst-gnu2-tls1mod.so-no-z-defs = yes
>>  CFLAGS-tst-gnu2-tls1mod.c += -mtls-dialect=gnu2
>> +
> 
> Spurious whitespace change.  Or rather, missing CFLAGS for
> tst-auditmod17 to disable stack protector.  I expect the test to fail
> when building glibc with -fstack-protector-all.

I will check building with -fstack-protector-all and remove the 
spurious whitespace.

> 
>> diff --git a/elf/dl-open.c b/elf/dl-open.c
>> index a066f39bd0..66ec9d7ed5 100644
>> --- a/elf/dl-open.c
>> +++ b/elf/dl-open.c
>> @@ -771,7 +771,7 @@ dl_open_worker (void *a)
>>      {
>>        struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
>>  #ifdef SHARED
>> -      bool initial = libc_map->l_ns == LM_ID_BASE;
>> +      bool initial = libc_map != NULL ? libc_map->l_ns == LM_ID_BASE : false;
>>  #else
>>        /* In the static case, there is only one namespace, but it
>>  	 contains a secondary libc (the primary libc is statically
> 
> Looks okay to me.  The previous code was just broken.
> 
> Thanks,
> Florian
>
Andreas Schwab July 7, 2021, 7:51 p.m. UTC | #3 
On Jul 07 2021, Adhemerval Zanella via Libc-alpha wrote:

> @@ -771,7 +771,7 @@ dl_open_worker (void *a)
>      {
>        struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
>  #ifdef SHARED
> -      bool initial = libc_map->l_ns == LM_ID_BASE;
> +      bool initial = libc_map != NULL ? libc_map->l_ns == LM_ID_BASE : false;

         bool initial = libc_map != NULL && libc_map->l_ns == LM_ID_BASE;

Andreas.
Adhemerval Zanella Netto July 7, 2021, 7:57 p.m. UTC | #4 
On 07/07/2021 16:51, Andreas Schwab wrote:
> On Jul 07 2021, Adhemerval Zanella via Libc-alpha wrote:
> 
>> @@ -771,7 +771,7 @@ dl_open_worker (void *a)
>>      {
>>        struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
>>  #ifdef SHARED
>> -      bool initial = libc_map->l_ns == LM_ID_BASE;
>> +      bool initial = libc_map != NULL ? libc_map->l_ns == LM_ID_BASE : false;
> 
>          bool initial = libc_map != NULL && libc_map->l_ns == LM_ID_BASE;
> 
> Andreas.
> 

Ack.
Florian Weimer July 7, 2021, 8:02 p.m. UTC | #5 
* Andreas Schwab:

> On Jul 07 2021, Adhemerval Zanella via Libc-alpha wrote:
>
>> @@ -771,7 +771,7 @@ dl_open_worker (void *a)
>>      {
>>        struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
>>  #ifdef SHARED
>> -      bool initial = libc_map->l_ns == LM_ID_BASE;
>> +      bool initial = libc_map != NULL ? libc_map->l_ns == LM_ID_BASE : false;
>
>          bool initial = libc_map != NULL && libc_map->l_ns == LM_ID_BASE;

True … but:

This is only used by dlopen/dlmopen, right?  And even if dlmopen is
called from an auditor (to load another libc), it is *never* the initial
libc in the base namespace.

The actual base namespace libc is handled in elf/rtld.c:dl_main:

  /* Relocation is complete.  Perform early libc initialization.  This
     is the initial libc, even if audit modules have been loaded with
     other libcs.  */
  _dl_call_libc_early_init (GL(dl_ns)[LM_ID_BASE].libc_map, true);

And I think the dl_open_worker should mirror that and just do:

  if (!args->libc_already_loaded)
    /* This is never the initial libc because it has been loaded via
       dlmopen.  */
    _dl_call_libc_early_init (libc_map, false);

Thanks,
Florian
Florian Weimer July 7, 2021, 8:07 p.m. UTC | #6 
* Florian Weimer:

> * Andreas Schwab:
>
>> On Jul 07 2021, Adhemerval Zanella via Libc-alpha wrote:
>>
>>> @@ -771,7 +771,7 @@ dl_open_worker (void *a)
>>>      {
>>>        struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
>>>  #ifdef SHARED
>>> -      bool initial = libc_map->l_ns == LM_ID_BASE;
>>> +      bool initial = libc_map != NULL ? libc_map->l_ns == LM_ID_BASE : false;
>>
>>          bool initial = libc_map != NULL && libc_map->l_ns == LM_ID_BASE;
>
> True … but:
>
> This is only used by dlopen/dlmopen, right?  And even if dlmopen is
> called from an auditor (to load another libc), it is *never* the initial
> libc in the base namespace.
>
> The actual base namespace libc is handled in elf/rtld.c:dl_main:
>
>   /* Relocation is complete.  Perform early libc initialization.  This
>      is the initial libc, even if audit modules have been loaded with
>      other libcs.  */
>   _dl_call_libc_early_init (GL(dl_ns)[LM_ID_BASE].libc_map, true);
>
> And I think the dl_open_worker should mirror that and just do:
>
>   if (!args->libc_already_loaded)
>     /* This is never the initial libc because it has been loaded via
>        dlmopen.  */
>     _dl_call_libc_early_init (libc_map, false);

Eh, or rather:

  if (!args->libc_already_loaded)
    {
      struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
      /* This is never the initial libc because it has been loaded via
         dlmopen.  */
      _dl_call_libc_early_init (libc_map, false);
    }

(_dl_call_libc_early_init checks for a null link map.)

Thanks,
Florian
Adhemerval Zanella Netto July 8, 2021, 12:13 p.m. UTC | #7 
On 07/07/2021 17:07, Florian Weimer via Libc-alpha wrote:
> * Florian Weimer:
> 
>> * Andreas Schwab:
>>
>>> On Jul 07 2021, Adhemerval Zanella via Libc-alpha wrote:
>>>
>>>> @@ -771,7 +771,7 @@ dl_open_worker (void *a)
>>>>      {
>>>>        struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
>>>>  #ifdef SHARED
>>>> -      bool initial = libc_map->l_ns == LM_ID_BASE;
>>>> +      bool initial = libc_map != NULL ? libc_map->l_ns == LM_ID_BASE : false;
>>>
>>>          bool initial = libc_map != NULL && libc_map->l_ns == LM_ID_BASE;
>>
>> True … but:
>>
>> This is only used by dlopen/dlmopen, right?  And even if dlmopen is
>> called from an auditor (to load another libc), it is *never* the initial
>> libc in the base namespace.
>>
>> The actual base namespace libc is handled in elf/rtld.c:dl_main:
>>
>>   /* Relocation is complete.  Perform early libc initialization.  This
>>      is the initial libc, even if audit modules have been loaded with
>>      other libcs.  */
>>   _dl_call_libc_early_init (GL(dl_ns)[LM_ID_BASE].libc_map, true);
>>
>> And I think the dl_open_worker should mirror that and just do:
>>
>>   if (!args->libc_already_loaded)
>>     /* This is never the initial libc because it has been loaded via
>>        dlmopen.  */
>>     _dl_call_libc_early_init (libc_map, false);
> 
> Eh, or rather:
> 
>   if (!args->libc_already_loaded)
>     {
>       struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
>       /* This is never the initial libc because it has been loaded via
>          dlmopen.  */
>       _dl_call_libc_early_init (libc_map, false);
>     }
> 
> (_dl_call_libc_early_init checks for a null link map.)

I think this make sense and it also simplifes the code a bit. I will
adjust the patch.
diff mbox series

Patch

diff --git a/elf/Makefile b/elf/Makefile
index b1e01d9516..5214196de6 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -219,7 +219,7 @@  tests += restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-dlopen-self tst-auditmany tst-initfinilazyfail tst-dlopenfail \
 	 tst-dlopenfail-2 \
 	 tst-filterobj tst-filterobj-dlopen tst-auxobj tst-auxobj-dlopen \
-	 tst-audit14 tst-audit15 tst-audit16 \
+	 tst-audit14 tst-audit15 tst-audit16 tst-audit17 \
 	 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 \
@@ -361,6 +361,7 @@  modules-names += tst-gnu2-tls1mod
 $(objpfx)tst-gnu2-tls1: $(objpfx)tst-gnu2-tls1mod.so
 tst-gnu2-tls1mod.so-no-z-defs = yes
 CFLAGS-tst-gnu2-tls1mod.c += -mtls-dialect=gnu2
+
 endif
 ifeq (yes,$(have-protected-data))
 modules-names += tst-protected1moda tst-protected1modb
@@ -1467,6 +1468,15 @@  $(objpfx)tst-auditlogmod-3.so: $(libsupport)
 $(objpfx)tst-audit16.out: \
   $(objpfx)tst-auditlogmod-1.so $(objpfx)tst-auditlogmod-2.so \
   $(objpfx)tst-auditlogmod-3.so
+$(objpfx)tst-audit17.out: $(objpfx)tst-auditmod17.so
+# The test check if a audit library without libc.so on DT_NEEDED works as
+# intended, so it uses an explicit link rule.
+$(objpfx)tst-auditmod17.so: $(objpfx)tst-auditmod17.os
+	$(CC) -nostdlib -nostartfiles -shared -o $@.new \
+	$(filter-out $(map-file),$^)
+	$(call after-link,$@.new)
+	mv -f $@.new $@
+tst-audit17-ENV = LD_AUDIT=$(objpfx)tst-auditmod17.so
 
 # tst-sonamemove links against an older implementation of the library.
 LDFLAGS-tst-sonamemove-linkmod1.so = \
diff --git a/elf/dl-open.c b/elf/dl-open.c
index a066f39bd0..66ec9d7ed5 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -771,7 +771,7 @@  dl_open_worker (void *a)
     {
       struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
 #ifdef SHARED
-      bool initial = libc_map->l_ns == LM_ID_BASE;
+      bool initial = libc_map != NULL ? libc_map->l_ns == LM_ID_BASE : false;
 #else
       /* In the static case, there is only one namespace, but it
 	 contains a secondary libc (the primary libc is statically
diff --git a/elf/tst-audit17.c b/elf/tst-audit17.c
new file mode 100644
index 0000000000..92986699d4
--- /dev/null
+++ b/elf/tst-audit17.c
@@ -0,0 +1,25 @@ 
+/* Check DT_AUDIT with audit not linked against libc.
+   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/>.  */
+
+static int
+do_test (void)
+{
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/elf/tst-auditmod17.c b/elf/tst-auditmod17.c
new file mode 100644
index 0000000000..762de376e2
--- /dev/null
+++ b/elf/tst-auditmod17.c
@@ -0,0 +1,24 @@ 
+/* Check DT_AUDIT with audit not linked against libc.
+   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/>.  */
+
+unsigned int
+la_version (unsigned int version)
+{
+  return version;
+}
+