From dbfc83bdcab941ce04200f97879f2a79fd0f2a0b Mon Sep 17 00:00:00 2001 From: Qixing ksyx Xue Date: Thu, 25 May 2023 11:10:54 -0400 Subject: [PATCH] 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 Suggested-by: Carlos O'Donell Signed-off-by: Qixing ksyx Xue Reviewed-by: Siddhesh Poyarekar --- 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 + . */ + +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 + . */ + +#include +#include +#include +#include + +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 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