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posix: Fix posix_spawnp to not execute invalid binaries in non compat mode (BZ#23264) 

Current posix_spawnp implementation wrongly tries to execute invalid
binaries (for instance script without shebang) as a shell script in
non compat mode.  It was a regression introduced by
9ff72da471 when __spawni started to use
__execvpe instead of __execve (glibc __execvpe try to execute ENOEXEC
as shell script regardless).

This patch fixes it by using an internal symbol (__execvpex) with the
faulty semantic (since compat mode is handled by spawni.c itself).

It was reported by Daniel Drake on libc-help [1].

Checked on x86_64-linux-gnu and i686-linux-gnu.

	[BZ #23264]
	* include/unistd.h (__execvpex): New prototype.
	* posix/Makefile (tests): Add tst-spawn4.
	(tests-internal): Add tst-spawn4-compat.
	* posix/execvpe.c (__execvpe_common, __execvpex): New functions.
	* posix/tst-spawn4-compat.c: New file.
	* posix/tst-spawn4.c: Likewise.
	* sysdeps/unix/sysv/linux/spawni.c (__spawni): Do not interpret invalid
	binaries as shell scripts.
	* sysdeps/posix/spawni.c (__spawni): Likewise.

[1] https://sourceware.org/ml/libc-help/2018-06/msg00012.html
This commit is contained in:
Adhemerval Zanella 2018-06-06 14:07:34 -03:00
parent 67c0579669
commit 283d985122
8 changed files with 175 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
ChangeLog
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@ -1,3 +1,16 @@
2018-06-08 Adhemerval Zanella <adhemerval.zanella@linaro.org>
[BZ #23264]
* include/unistd.h (__execvpex): New prototype.
* posix/Makefile (tests): Add tst-spawn4.
(tests-internal): Add tst-spawn4-compat.
* posix/execvpe.c (__execvpe_common, __execvpex): New functions.
* posix/tst-spawn4-compat.c: New file.
* posix/tst-spawn4.c: Likewise.
* sysdeps/unix/sysv/linux/spawni.c (__spawni): Do not interpret invalid
binaries as shell scripts.
* sysdeps/posix/spawni.c (__spawni): Likewise.
2018-06-08 H.J. Lu <hongjiu.lu@intel.com>
[BZ #23145]

2
include/unistd.h
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@ -77,6 +77,8 @@ extern char *__getcwd (char *__buf, size_t __size) attribute_hidden;
extern int __rmdir (const char *__path) attribute_hidden;
extern int __execvpe (const char *file, char *const argv[],
char *const envp[]) attribute_hidden;
extern int __execvpex (const char *file, char *const argv[],
char *const envp[]) attribute_hidden;
/* Get the canonical absolute name of the named directory, and put it in SIZE
bytes of BUF. Returns NULL if the directory couldn't be determined or

4
posix/Makefile
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@ -95,10 +95,10 @@ tests := test-errno tstgetopt testfnm runtests runptests \
tst-posix_spawn-fd tst-posix_spawn-setsid \
tst-posix_fadvise tst-posix_fadvise64 \
tst-sysconf-empty-chroot tst-glob_symlinks tst-fexecve \
tst-glob-tilde test-ssize-max
tst-glob-tilde test-ssize-max tst-spawn4
tests-internal := bug-regex5 bug-regex20 bug-regex33 \
tst-rfc3484 tst-rfc3484-2 tst-rfc3484-3 \
tst-glob_lstat_compat
tst-glob_lstat_compat tst-spawn4-compat
xtests := bug-ga2 tst-getaddrinfo4 tst-getaddrinfo5
ifeq (yes,$(build-shared))
test-srcs := globtest

26
posix/execvpe.c
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@ -67,11 +67,9 @@ maybe_script_execute (const char *file, char *const argv[], char *const envp[])
__execve (new_argv[0], new_argv, envp);
}
/* Execute FILE, searching in the `PATH' environment variable if it contains
no slashes, with arguments ARGV and environment from ENVP. */
int
__execvpe (const char *file, char *const argv[], char *const envp[])
static int
__execvpe_common (const char *file, char *const argv[], char *const envp[],
bool exec_script)
{
/* We check the simple case first. */
if (*file == '\0')
@ -85,7 +83,7 @@ __execvpe (const char *file, char *const argv[], char *const envp[])
{
__execve (file, argv, envp);
if (errno == ENOEXEC)
if (errno == ENOEXEC && exec_script)
maybe_script_execute (file, argv, envp);
return -1;
@ -137,7 +135,7 @@ __execvpe (const char *file, char *const argv[], char *const envp[])
__execve (buffer, argv, envp);
if (errno == ENOEXEC)
if (errno == ENOEXEC && exec_script)
/* This has O(P*C) behavior, where P is the length of the path and C
is the argument count. A better strategy would be allocate the
substitute argv and reuse it each time through the loop (so it
@ -184,4 +182,18 @@ __execvpe (const char *file, char *const argv[], char *const envp[])
return -1;
}
/* Execute FILE, searching in the `PATH' environment variable if it contains
no slashes, with arguments ARGV and environment from ENVP. */
int
__execvpe (const char *file, char *const argv[], char *const envp[])
{
return __execvpe_common (file, argv, envp, true);
}
weak_alias (__execvpe, execvpe)
/* Same as __EXECVPE, but does not try to execute NOEXEC files. */
int
__execvpex (const char *file, char *const argv[], char *const envp[])
{
return __execvpe_common (file, argv, envp, false);
}

77
posix/tst-spawn4-compat.c Normal file
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@ -0,0 +1,77 @@
/* Check if posix_spawn does handle correctly ENOEXEC files.
Copyright (C) 2018 Free Software Foundation, Inc.
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 <spawn.h>
#include <errno.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <support/xunistd.h>
#include <support/check.h>
#include <support/temp_file.h>
#include <shlib-compat.h>
#if TEST_COMPAT (libc, GLIBC_2_0, GLIBC_2_15)
compat_symbol_reference (libc, posix_spawn, posix_spawn, GLIBC_2_2);
compat_symbol_reference (libc, posix_spawnp, posix_spawnp, GLIBC_2_2);
static int
do_test (void)
{
char *scriptname;
int fd = create_temp_file ("tst-spawn4.", &scriptname);
TEST_VERIFY_EXIT (fd >= 0);
const char script[] = "exit 65";
xwrite (fd, script, sizeof (script) - 1);
xclose (fd);
TEST_VERIFY_EXIT (chmod (scriptname, 0x775) == 0);
pid_t pid;
int status;
/* For compat symbol it verifies that trying to issued a shell script
without a shebang is correctly executed. */
status = posix_spawn (&pid, scriptname, NULL, NULL, (char *[]) { 0 },
(char *[]) { 0 });
TEST_VERIFY_EXIT (status == 0);
TEST_VERIFY_EXIT (waitpid (pid, &status, 0) == pid);
TEST_VERIFY_EXIT (WIFEXITED (status) == 1 && WEXITSTATUS (status) == 65);
status = posix_spawnp (&pid, scriptname, NULL, NULL, (char *[]) { 0 },
(char *[]) { 0 });
TEST_VERIFY_EXIT (status == 0);
TEST_VERIFY_EXIT (waitpid (pid, &status, 0) == pid);
TEST_VERIFY_EXIT (WIFEXITED (status) == 1 && WEXITSTATUS (status) == 65);
return 0;
}
#else
static int
do_test (void)
{
return 77;
}
#endif
#include <support/test-driver.c>

56
posix/tst-spawn4.c Normal file
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@ -0,0 +1,56 @@
/* Check if posix_spawn does handle correctly ENOEXEC files.
Copyright (C) 2018 Free Software Foundation, Inc.
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 <spawn.h>
#include <errno.h>
#include <unistd.h>
#include <sys/stat.h>
#include <support/xunistd.h>
#include <support/check.h>
#include <support/temp_file.h>
static int
do_test (void)
{
char *scriptname;
int fd = create_temp_file ("tst-spawn4.", &scriptname);
TEST_VERIFY_EXIT (fd >= 0);
const char script[] = "echo it should not happen";
xwrite (fd, script, sizeof (script) - 1);
xclose (fd);
TEST_VERIFY_EXIT (chmod (scriptname, 0x775) == 0);
pid_t pid;
int status;
/* Check if scripts without shebang are correctly not executed. */
status = posix_spawn (&pid, scriptname, NULL, NULL, (char *[]) { 0 },
(char *[]) { 0 });
TEST_VERIFY_EXIT (status == ENOEXEC);
status = posix_spawnp (&pid, scriptname, NULL, NULL, (char *[]) { 0 },
(char *[]) { 0 });
TEST_VERIFY_EXIT (status == ENOEXEC);
return 0;
}
#include <support/test-driver.c>

4
sysdeps/posix/spawni.c
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@ -310,6 +310,8 @@ __spawni (pid_t * pid, const char *file,
const posix_spawnattr_t * attrp, char *const argv[],
char *const envp[], int xflags)
{
/* It uses __execvpex to avoid run ENOEXEC in non compatibility mode (it
will be handled by maybe_script_execute). */
return __spawnix (pid, file, acts, attrp, argv, envp, xflags,
xflags & SPAWN_XFLAGS_USE_PATH ? __execvpe : __execve);
xflags & SPAWN_XFLAGS_USE_PATH ? __execvpex : __execve);
}

4
sysdeps/unix/sysv/linux/spawni.c
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@ -404,6 +404,8 @@ __spawni (pid_t * pid, const char *file,
const posix_spawnattr_t * attrp, char *const argv[],
char *const envp[], int xflags)
{
/* It uses __execvpex to avoid run ENOEXEC in non compatibility mode (it
will be handled by maybe_script_execute). */
return __spawnix (pid, file, acts, attrp, argv, envp, xflags,
xflags & SPAWN_XFLAGS_USE_PATH ? __execvpe : __execve);
xflags & SPAWN_XFLAGS_USE_PATH ? __execvpex :__execve);
}