glibc/elf/tst-rootdir-lib.c

/* 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";
}
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> 2023-05-25 15:10:54 +00:00			`/* 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";`
			`}`