diff mbox series

[v3] elf: Add test for locating libraries in root dir (bug 30435)

Message ID ME2P282MB224207E3DA9DD0B845062C28B4469@ME2P282MB2242.AUSP282.PROD.OUTLOOK.COM
State Committed
Commit dbfc83bdcab941ce04200f97879f2a79fd0f2a0b
Headers
Series [v3] elf: Add test for locating libraries in root dir (bug 30435) |

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Context Check Description
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Commit Message

Qixing ksyx Xue May 25, 2023, 2:56 p.m. UTC 
  When dlopen is being called, efforts have been made to improve
future lookup performance. This includes marking a search path
as non-existent using `stat`. However, if the root directory
is given as a search path, there exists a bug which erroneously
marks it as non-existing.

The bug is reproduced under the following sequence:

  1. dlopen is called to open a shared library, with at least:
     1) a dependency 'A.so' not directly under the '/' directory
        (e.g. /lib/A.so), and
     2) another dependency 'B.so' resides in '/'.
  2. for this bug to reproduce, 'A.so' should be searched *before* 'B.so'.
  3. it first tries to find 'A.so' in /, (e.g. /A.so):
     - this will (obviously) fail,
     - since it's the first time we have seen the '/' directory,
       its 'status' is 'unknown'.
  4. `buf[buflen - namelen - 1] = '\0'` is executed:
     - it intends to remove the leaf and its final slash,
     - because of the speciality of '/', its buflen == namelen + 1,
     - it erroneously clears the entire buffer.
  6. it then calls 'stat' with the empty buffer:
     - which will result in an error.
  7. so it marks '/' as 'nonexisting', future lookups will not consider
     this path.
  8. while /B.so *does* exist, failure to look it up in the '/'
     directory leads to a 'cannot open shared object file' error.

This patch fixes the bug by preventing 'buflen', an index to put '\0',
from being set to 0, so that the root '/' is always kept.
Relative search paths are always considered as 'existing' so this
wont be affected.

Writeup by Moody Liu <mooodyhunter@outlook.com>

Suggested-by: Carlos O'Donell <carlos@redhat.com>
Signed-off-by: Qixing ksyx Xue <qixingxue@outlook.com>
---
 elf/Makefile                      |  3 +++
 elf/tst-rootdir-lib.c             | 23 +++++++++++++++++++
 elf/tst-rootdir.c                 | 37 +++++++++++++++++++++++++++++++
 elf/tst-rootdir.root/preclean.req |  0
 elf/tst-rootdir.script            |  1 +
 5 files changed, 64 insertions(+)
 create mode 100644 elf/tst-rootdir-lib.c
 create mode 100644 elf/tst-rootdir.c
 create mode 100644 elf/tst-rootdir.root/preclean.req
 create mode 100644 elf/tst-rootdir.script

Comments

Siddhesh Poyarekar May 25, 2023, 3:12 p.m. UTC | #1 
On 2023-05-25 10:56, Qixing ksyx Xue wrote:
> When dlopen is being called, efforts have been made to improve
> future lookup performance. This includes marking a search path
> as non-existent using `stat`. However, if the root directory
> is given as a search path, there exists a bug which erroneously
> marks it as non-existing.
> 
> The bug is reproduced under the following sequence:
> 
>    1. dlopen is called to open a shared library, with at least:
>       1) a dependency 'A.so' not directly under the '/' directory
>          (e.g. /lib/A.so), and
>       2) another dependency 'B.so' resides in '/'.
>    2. for this bug to reproduce, 'A.so' should be searched *before* 'B.so'.
>    3. it first tries to find 'A.so' in /, (e.g. /A.so):
>       - this will (obviously) fail,
>       - since it's the first time we have seen the '/' directory,
>         its 'status' is 'unknown'.
>    4. `buf[buflen - namelen - 1] = '\0'` is executed:
>       - it intends to remove the leaf and its final slash,
>       - because of the speciality of '/', its buflen == namelen + 1,
>       - it erroneously clears the entire buffer.
>    6. it then calls 'stat' with the empty buffer:
>       - which will result in an error.
>    7. so it marks '/' as 'nonexisting', future lookups will not consider
>       this path.
>    8. while /B.so *does* exist, failure to look it up in the '/'
>       directory leads to a 'cannot open shared object file' error.
> 
> This patch fixes the bug by preventing 'buflen', an index to put '\0',
> from being set to 0, so that the root '/' is always kept.
> Relative search paths are always considered as 'existing' so this
> wont be affected.
> 
> Writeup by Moody Liu <mooodyhunter@outlook.com>
> 
> Suggested-by: Carlos O'Donell <carlos@redhat.com>
> Signed-off-by: Qixing ksyx Xue <qixingxue@outlook.com>

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

I'll test and commit this shortly.

Thanks,
Sid

> ---
>   elf/Makefile                      |  3 +++
>   elf/tst-rootdir-lib.c             | 23 +++++++++++++++++++
>   elf/tst-rootdir.c                 | 37 +++++++++++++++++++++++++++++++
>   elf/tst-rootdir.root/preclean.req |  0
>   elf/tst-rootdir.script            |  1 +
>   5 files changed, 64 insertions(+)
>   create mode 100644 elf/tst-rootdir-lib.c
>   create mode 100644 elf/tst-rootdir.c
>   create mode 100644 elf/tst-rootdir.root/preclean.req
>   create mode 100644 elf/tst-rootdir.script
> 
> diff --git a/elf/Makefile b/elf/Makefile
> index e262f3e6b1..8640138a72 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -325,6 +325,7 @@ static-dlopen-environment = \
>     LD_LIBRARY_PATH=$(ld-library-path):$(common-objpfx)dlfcn
>   tst-tls9-static-ENV = $(static-dlopen-environment)
>   tst-single_threaded-static-dlopen-ENV = $(static-dlopen-environment)
> +tst-rootdir-ENV = LD_LIBRARY_PATH=/
>   
>   tests += \
>     argv0test \
> @@ -506,6 +507,7 @@ tests-container += \
>     tst-dlopen-tlsmodid-container \
>     tst-pldd \
>     tst-preload-pthread-libc \
> +  tst-rootdir \
>     # tests-container
>   
>   test-srcs = \
> @@ -855,6 +857,7 @@ modules-names += \
>     tst-relsort1mod1 \
>     tst-relsort1mod2 \
>     tst-ro-dynamic-mod \
> +  tst-rootdir-lib \
>     tst-single_threaded-mod1 \
>     tst-single_threaded-mod2 \
>     tst-single_threaded-mod3 \
> diff --git a/elf/tst-rootdir-lib.c b/elf/tst-rootdir-lib.c
> new file mode 100644
> index 0000000000..007c4b0095
> --- /dev/null
> +++ b/elf/tst-rootdir-lib.c
> @@ -0,0 +1,23 @@
> +/* Simple library for testing locating library in root directories.
> +   Copyright The GNU Toolchain Authors.
> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +const char *
> +test_func (void)
> +{
> +  return "Success";
> +}
> diff --git a/elf/tst-rootdir.c b/elf/tst-rootdir.c
> new file mode 100644
> index 0000000000..83284ea59e
> --- /dev/null
> +++ b/elf/tst-rootdir.c
> @@ -0,0 +1,37 @@
> +/* Test code for locating libraries in root directories.
> +   Copyright The GNU Toolchain Authors.
> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <support/test-driver.h>
> +#include <support/check.h>
> +#include <dlfcn.h>
> +#include <assert.h>
> +
> +static int
> +do_test (void)
> +{
> +  void *handle = dlopen ("libtest.so", RTLD_LAZY);
> +  TEST_VERIFY_EXIT (handle != NULL);
> +  typedef const char *(test_func_t) (void);
> +  test_func_t *func = dlsym (handle, "test_func");
> +  assert (func != NULL);
> +  TEST_COMPARE_STRING (func (), "Success");
> +  dlclose (handle);
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
> diff --git a/elf/tst-rootdir.root/preclean.req b/elf/tst-rootdir.root/preclean.req
> new file mode 100644
> index 0000000000..e69de29bb2
> diff --git a/elf/tst-rootdir.script b/elf/tst-rootdir.script
> new file mode 100644
> index 0000000000..f852c0ec34
> --- /dev/null
> +++ b/elf/tst-rootdir.script
> @@ -0,0 +1 @@
> +cp $B/elf/tst-rootdir-lib.so /libtest.so
diff mbox series

Patch

diff --git a/elf/Makefile b/elf/Makefile
index e262f3e6b1..8640138a72 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -325,6 +325,7 @@  static-dlopen-environment = \
   LD_LIBRARY_PATH=$(ld-library-path):$(common-objpfx)dlfcn
 tst-tls9-static-ENV = $(static-dlopen-environment)
 tst-single_threaded-static-dlopen-ENV = $(static-dlopen-environment)
+tst-rootdir-ENV = LD_LIBRARY_PATH=/
 
 tests += \
   argv0test \
@@ -506,6 +507,7 @@  tests-container += \
   tst-dlopen-tlsmodid-container \
   tst-pldd \
   tst-preload-pthread-libc \
+  tst-rootdir \
   # tests-container
 
 test-srcs = \
@@ -855,6 +857,7 @@  modules-names += \
   tst-relsort1mod1 \
   tst-relsort1mod2 \
   tst-ro-dynamic-mod \
+  tst-rootdir-lib \
   tst-single_threaded-mod1 \
   tst-single_threaded-mod2 \
   tst-single_threaded-mod3 \
diff --git a/elf/tst-rootdir-lib.c b/elf/tst-rootdir-lib.c
new file mode 100644
index 0000000000..007c4b0095
--- /dev/null
+++ b/elf/tst-rootdir-lib.c
@@ -0,0 +1,23 @@ 
+/* Simple library for testing locating library in root directories.
+   Copyright The GNU Toolchain Authors.
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+const char *
+test_func (void)
+{
+  return "Success";
+}
diff --git a/elf/tst-rootdir.c b/elf/tst-rootdir.c
new file mode 100644
index 0000000000..83284ea59e
--- /dev/null
+++ b/elf/tst-rootdir.c
@@ -0,0 +1,37 @@ 
+/* Test code for locating libraries in root directories.
+   Copyright The GNU Toolchain Authors.
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/test-driver.h>
+#include <support/check.h>
+#include <dlfcn.h>
+#include <assert.h>
+
+static int
+do_test (void)
+{
+  void *handle = dlopen ("libtest.so", RTLD_LAZY);
+  TEST_VERIFY_EXIT (handle != NULL);
+  typedef const char *(test_func_t) (void);
+  test_func_t *func = dlsym (handle, "test_func");
+  assert (func != NULL);
+  TEST_COMPARE_STRING (func (), "Success");
+  dlclose (handle);
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/elf/tst-rootdir.root/preclean.req b/elf/tst-rootdir.root/preclean.req
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/elf/tst-rootdir.script b/elf/tst-rootdir.script
new file mode 100644
index 0000000000..f852c0ec34
--- /dev/null
+++ b/elf/tst-rootdir.script
@@ -0,0 +1 @@ 
+cp $B/elf/tst-rootdir-lib.so /libtest.so