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elf: Add test for locating libraries in root dir (bug 30435)
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>
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@ -325,6 +325,7 @@ static-dlopen-environment = \
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LD_LIBRARY_PATH=$(ld-library-path):$(common-objpfx)dlfcn
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tst-tls9-static-ENV = $(static-dlopen-environment)
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tst-single_threaded-static-dlopen-ENV = $(static-dlopen-environment)
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tst-rootdir-ENV = LD_LIBRARY_PATH=/
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tests += \
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argv0test \
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@ -506,6 +507,7 @@ tests-container += \
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tst-dlopen-tlsmodid-container \
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tst-pldd \
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tst-preload-pthread-libc \
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tst-rootdir \
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# tests-container
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test-srcs = \
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@ -855,6 +857,7 @@ modules-names += \
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tst-relsort1mod1 \
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tst-relsort1mod2 \
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tst-ro-dynamic-mod \
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tst-rootdir-lib \
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tst-single_threaded-mod1 \
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tst-single_threaded-mod2 \
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tst-single_threaded-mod3 \
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23
elf/tst-rootdir-lib.c
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23
elf/tst-rootdir-lib.c
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@ -0,0 +1,23 @@
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/* Simple library for testing locating library in root directories.
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Copyright The GNU Toolchain Authors.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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const char *
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test_func (void)
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{
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return "Success";
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}
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37
elf/tst-rootdir.c
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37
elf/tst-rootdir.c
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@ -0,0 +1,37 @@
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/* Test code for locating libraries in root directories.
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Copyright The GNU Toolchain Authors.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <support/test-driver.h>
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#include <support/check.h>
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#include <dlfcn.h>
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#include <assert.h>
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static int
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do_test (void)
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{
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void *handle = dlopen ("libtest.so", RTLD_LAZY);
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TEST_VERIFY_EXIT (handle != NULL);
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typedef const char *(test_func_t) (void);
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test_func_t *func = dlsym (handle, "test_func");
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assert (func != NULL);
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TEST_COMPARE_STRING (func (), "Success");
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dlclose (handle);
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return 0;
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}
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#include <support/test-driver.c>
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0
elf/tst-rootdir.root/preclean.req
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0
elf/tst-rootdir.root/preclean.req
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1
elf/tst-rootdir.script
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1
elf/tst-rootdir.script
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@ -0,0 +1 @@
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cp $B/elf/tst-rootdir-lib.so /libtest.so
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