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gdb: check for empty strings in get_standard_cache_dir/get_standard_config_dir

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As reported in PR 27157, if some environment variables read at startup
by GDB are defined but empty, we hit the assert in gdb_abspath:

    $ XDG_CACHE_HOME= ./gdb -nx --data-directory=data-directory -q
    AddressSanitizer:DEADLYSIGNAL
    =================================================================
    ==2007040==ERROR: AddressSanitizer: SEGV on unknown address 0x0000000001b0 (pc 0x5639d4aa4127 bp 0x7ffdac232c00 sp 0x7ffdac232bf0 T0)
    ==2007040==The signal is caused by a READ memory access.
    ==2007040==Hint: address points to the zero page.
        #0 0x5639d4aa4126 in target_stack::top() const /home/smarchi/src/binutils-gdb/gdb/target.h:1334
        #1 0x5639d4aa41f1 in inferior::top_target() /home/smarchi/src/binutils-gdb/gdb/inferior.h:369
        #2 0x5639d4a70b1f in current_top_target() /home/smarchi/src/binutils-gdb/gdb/target.c:120
        #3 0x5639d4b00591 in gdb_readline_wrapper_cleanup::gdb_readline_wrapper_cleanup() /home/smarchi/src/binutils-gdb/gdb/top.c:1046
        #4 0x5639d4afab31 in gdb_readline_wrapper(char const*) /home/smarchi/src/binutils-gdb/gdb/top.c:1104
        #5 0x5639d4ccce2c in defaulted_query /home/smarchi/src/binutils-gdb/gdb/utils.c:893
        #6 0x5639d4ccd6af in query(char const*, ...) /home/smarchi/src/binutils-gdb/gdb/utils.c:985
        #7 0x5639d4ccaec1 in internal_vproblem /home/smarchi/src/binutils-gdb/gdb/utils.c:373
        #8 0x5639d4ccb3d1 in internal_verror(char const*, int, char const*, __va_list_tag*) /home/smarchi/src/binutils-gdb/gdb/utils.c:439
        #9 0x5639d5151a92 in internal_error(char const*, int, char const*, ...) /home/smarchi/src/binutils-gdb/gdbsupport/errors.cc:55
        #10 0x5639d5162ab4 in gdb_abspath(char const*) /home/smarchi/src/binutils-gdb/gdbsupport/pathstuff.cc:132
        #11 0x5639d5162fac in get_standard_cache_dir[abi:cxx11]() /home/smarchi/src/binutils-gdb/gdbsupport/pathstuff.cc:228
        #12 0x5639d3e76a81 in _initialize_index_cache() /home/smarchi/src/binutils-gdb/gdb/dwarf2/index-cache.c:325
        #13 0x5639d4dbbe92 in initialize_all_files() /home/smarchi/build/binutils-gdb/gdb/init.c:321
        #14 0x5639d4b00259 in gdb_init(char*) /home/smarchi/src/binutils-gdb/gdb/top.c:2344
        #15 0x5639d4440715 in captured_main_1 /home/smarchi/src/binutils-gdb/gdb/main.c:950
        #16 0x5639d444252e in captured_main /home/smarchi/src/binutils-gdb/gdb/main.c:1229
        #17 0x5639d44425cf in gdb_main(captured_main_args*) /home/smarchi/src/binutils-gdb/gdb/main.c:1254
        #18 0x5639d3923371 in main /home/smarchi/src/binutils-gdb/gdb/gdb.c:32
        #19 0x7fa002d3f0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
        #20 0x5639d392314d in _start (/home/smarchi/build/binutils-gdb/gdb/gdb+0x4d414d)

gdb_abspath doesn't handle empty strings, so handle this case in the
callers.  If a variable is defined but empty, I think it's reasonable in
this case to just ignore it, as if it was not defined.

Note that this sometimes also lead to a segfault, because the failed
assertion happens very early during startup, before things are fully
initialized.

gdbsupport/ChangeLog:

	PR gdb/27157
	* pathstuff.cc (get_standard_cache_dir, get_standard_config_dir,
	find_gdb_home_config_file): Add empty string check.

gdb/testsuite/ChangeLog:

	PR gdb/27157
	* gdb.base/empty-host-env-vars.exp: New test.

Change-Id: I8654d8e97e74e1dff6d308c111ae4b1bbf07bef9
This commit is contained in:
Simon Marchi 2021-01-08 13:46:56 -05:00
parent d00f086803
commit 6abd4cf281
4 changed files with 90 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
gdb/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2021-01-08 Simon Marchi <simon.marchi@polymtl.ca>
PR gdb/27157
* gdb.base/empty-host-env-vars.exp: New test.
2021-01-08 Andrew Burgess <andrew.burgess@embecosm.com>
* gdb.base/completion.exp: Add a new test.

72
gdb/testsuite/gdb.base/empty-host-env-vars.exp Normal file
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@ -0,0 +1,72 @@
# Copyright 2021 Free Software Foundation, Inc.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# GDB reads some environment variables on startup, make sure it behaves
# correctly if these variables are defined but empty.
set all_env_vars { HOME XDG_CACHE_HOME LOCALAPPDATA XDG_CONFIG_HOME }
# Record the initial value of the index-cache directory.
clean_restart
set index_cache_directory ""
gdb_test_multiple "show index-cache directory" "" {
-re -wrap "The directory of the index cache is \"(.*)\"\\." {
set index_cache_directory $expect_out(1,string)
set index_cache_directory [string_to_regexp $index_cache_directory]
pass $gdb_test_name
}
}
foreach_with_prefix env_var_name $all_env_vars {
# Restore the original state of the environment variable.
save_vars env($env_var_name) {
set env($env_var_name) {}
clean_restart
# Verify that the empty environment variable didn't affect the
# index-cache directory setting, that we still see the initial value.
# "HOME" is different, because if that one is unset, GDB isn't even
# able to compute the default location. In that case, we expect it to
# be empty.
if { $env_var_name == "HOME" } {
gdb_test "show index-cache directory" \
"The directory of the index cache is \"\"\\."
} else {
gdb_test "show index-cache directory" \
"The directory of the index cache is \"$index_cache_directory\"\\."
}
}
}
# Try the same, but with all the env vars set to an empty value at the same
# time.
with_test_prefix "all env vars" {
set save_vars_arg {}
foreach env_var_name $all_env_vars {
lappend save_vars_arg env($env_var_name)
}
# Restore the original state of all the environment variables.
save_vars $save_vars_arg {
foreach env_var_name $all_env_vars {
set env($env_var_name) {}
}
clean_restart
gdb_test "show index-cache directory" \
"The directory of the index cache is \"\"\\."
}
}

6
gdbsupport/ChangeLog
View File

@ -1,3 +1,9 @@
2021-01-08 Simon Marchi <simon.marchi@polymtl.ca>
PR gdb/27157
* pathstuff.cc (get_standard_cache_dir, get_standard_config_dir,
find_gdb_home_config_file): Add empty string check.
2021-01-06 Mike Frysinger <vapier@gentoo.org>
* common-utils.h (align_up): Fix typo in header comment.

14
gdbsupport/pathstuff.cc
View File

@ -222,7 +222,7 @@ get_standard_cache_dir ()
#ifndef __APPLE__
const char *xdg_cache_home = getenv ("XDG_CACHE_HOME");
if (xdg_cache_home != NULL)
if (xdg_cache_home != NULL && xdg_cache_home[0] != '\0')
{
/* Make sure the path is absolute and tilde-expanded. */
gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (xdg_cache_home));
@ -231,7 +231,7 @@ get_standard_cache_dir ()
#endif
const char *home = getenv ("HOME");
if (home != NULL)
if (home != NULL && home[0] != '\0')
{
/* Make sure the path is absolute and tilde-expanded. */
gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (home));
@ -240,14 +240,14 @@ get_standard_cache_dir ()
#ifdef WIN32
const char *win_home = getenv ("LOCALAPPDATA");
if (win_home != NULL)
if (win_home != NULL && win_home[0] != '\0')
{
/* Make sure the path is absolute and tilde-expanded. */
gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (win_home));
return string_printf ("%s/gdb", abs.get ());
}
#endif
return {};
}
@ -289,7 +289,7 @@ get_standard_config_dir ()
#ifndef __APPLE__
const char *xdg_config_home = getenv ("XDG_CONFIG_HOME");
if (xdg_config_home != NULL)
if (xdg_config_home != NULL && xdg_config_home[0] != '\0')
{
/* Make sure the path is absolute and tilde-expanded. */
gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (xdg_config_home));
@ -298,7 +298,7 @@ get_standard_config_dir ()
#endif
const char *home = getenv ("HOME");
if (home != NULL)
if (home != NULL && home[0] != '\0')
{
/* Make sure the path is absolute and tilde-expanded. */
gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (home));
@ -340,7 +340,7 @@ find_gdb_home_config_file (const char *name, struct stat *buf)
}
const char *homedir = getenv ("HOME");
if (homedir != nullptr)
if (homedir != nullptr && homedir[0] != '\0')
{
/* Make sure the path is absolute and tilde-expanded. */
gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (homedir));