d/freebsd-nq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Replace basename(3) by a thread-safe implementation.

Browse Source 
Now that the changes to the dirname(3) function had some time to settle,
let's go ahead and use the same approach for replacing basename(3) by a
simple implementation that modifies the input string, thereby making it
thread-safe and guaranteed to succeed.

Unlike dirname(3), this function already had a thread-safe variant
basename_r(3). This function had its own set of problems, like having an
upper bound on the pathname length. Keep this function around for
compatibility, but remove most references from the man page. Make the
man page more similar to that of dirname(3).

As the basename_r(3) function is only provided by FreeBSD (and Bionic),
depending on its use is even more implementation defined than assuming
that basename(3) is thread-safe.

Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D8382
This commit is contained in:
Ed Schouten 2016-11-03 20:21:34 +00:00
parent 1bec4c5b3d
commit 34168b28e9
6 changed files with 155 additions and 128 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
include/libgen.h
View File

@ -40,21 +40,24 @@ char *dirname(char *);
__END_DECLS
/*
* In FreeBSD 12, the prototype of dirname() was modified to comply to
* POSIX. This function may now modify its input. Unfortunately, our
* copy of xinstall(8) shipped with previous versions of FreeBSD is
* built using the host headers and libc during the bootstrapping phase
* and depends on the old behavior.
* In FreeBSD 12, the prototypes of basename() and dirname() were
* modified to comply to POSIX. These functions may now modify their
* input. Unfortunately, our copy of xinstall(8) shipped with previous
* versions of FreeBSD is built using the host headers and libc during
* the bootstrapping phase and depends on the old behavior.
*
* Apply a workaround where we explicitly link against dirname@FBSD_1.0
* in case this function is called on constant strings, instead of
* making the program crash at runtime.
* Apply a workaround where we explicitly link against basename@FBSD_1.0
* and dirname@FBSD_1.0 in case these functions are called on constant
* strings, instead of making the program crash at runtime.
*/
#if defined(__generic) && !defined(__cplusplus)
__BEGIN_DECLS
char *__old_basename(char *);
char *__old_dirname(char *);
__END_DECLS
__sym_compat(basename, __old_basename, FBSD_1.0);
__sym_compat(dirname, __old_dirname, FBSD_1.0);
#define basename(x) __generic(x, const char *, __old_basename, basename)(x)
#define dirname(x) __generic(x, const char *, __old_dirname, dirname)(x)
#endif

1
lib/libc/gen/Makefile.inc
View File

@ -17,6 +17,7 @@ SRCS+= __getosreldate.c \
assert.c \
auxv.c \
basename.c \
basename_compat.c \
cap_sandboxed.c \
check_utility_compat.c \
clock.c \

2
lib/libc/gen/Symbol.map
View File

@ -68,7 +68,6 @@ FBSD_1.0 {
arc4random_addrandom;
arc4random_stir;
__assert;
basename;
check_utility_compat;
clock;
closedir;
@ -414,6 +413,7 @@ FBSD_1.4 {
};
FBSD_1.5 {
basename;
dirname;
};

79
lib/libc/gen/basename.3
View File

@ -16,7 +16,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd July 29, 2016
.Dd October 29, 2016
.Dt BASENAME 3
.Os
.Sh NAME
@ -26,8 +26,6 @@
.In libgen.h
.Ft char *
.Fn basename "char *path"
.Ft char *
.Fn basename_r "const char *path" "char *bname"
.Sh DESCRIPTION
The
.Fn basename
@ -36,6 +34,7 @@ function returns the last component from the pathname pointed to by
deleting any trailing
.Sq \&/
characters.
.Sh RETURN VALUES
If
.Fa path
consists entirely of
@ -48,48 +47,19 @@ If
is a null pointer or the empty string, a pointer to the string
.Qq \&.
is returned.
.Pp
The
.Fn basename_r
variation accepts a buffer of at least
.Dv MAXPATHLEN
bytes in which to store the resulting component.
.Sh IMPLEMENTATION NOTES
The
.Fn basename
function
returns a pointer to internal storage space allocated on the first call
that will be overwritten
by subsequent calls.
.Pp
Other vendor implementations of
.Fn basename
may store their result in the input buffer,
making it safe to use in multithreaded applications.
Future versions of
.Fx
will follow this approach as well.
.Fn basename_r
will then become obsolete.
.Sh RETURN VALUES
On successful completion,
.Fn basename
and
.Fn basename_r
return pointers to the last component of
Otherwise,
it returns a pointer to the last component of
.Fa path .
.Pp
If they fail, a null pointer is returned and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
The following error codes may be set in
.Va errno :
.Bl -tag -width Er
.It Bq Er ENAMETOOLONG
The path component to be returned was larger than
.Dv MAXPATHLEN .
.El
.Sh IMPLEMENTATION NOTES
This implementation of
.Fn basename
uses the buffer provided by the caller to store the resulting pathname
component.
Other vendor implementations may return a pointer to internal storage
space instead.
The advantage of the former approach is that it ensures thread-safety,
while also placing no upper limit on the supported length of the
pathname.
.Sh SEE ALSO
.Xr basename 1 ,
.Xr dirname 1 ,
@ -106,16 +76,13 @@ function first appeared in
.Ox 2.2
and
.Fx 4.2 .
.Sh AUTHORS
.An Todd C. Miller
.Sh CAVEATS
.Fn basename
returns a pointer to internal static storage space that will be overwritten
by subsequent calls.
.Pp
Other vendor implementations of
.Fn basename
may modify the contents of the string passed to
.Fn basename ;
this should be taken into account when writing code which calls this function
if portability is desired.
In
.Fx 12.0 ,
this function was reimplemented to store its result in the provided
input buffer.
There is no longer any need to use the
.Fn basename_r
function.
.Sh AUTHORS
.An Nuxi, the Netherlands

101
lib/libc/gen/basename.c
View File

@ -1,79 +1,54 @@
/* $OpenBSD: basename.c,v 1.14 2005/08/08 08:05:33 espie Exp $ */
/*
* Copyright (c) 1997, 2004 Todd C. Miller <Todd.Miller@courtesan.com>
/*-
* Copyright (c) 2015-2016 Nuxi, https://nuxi.nl/
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <errno.h>
#include <libgen.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
char *
basename_r(const char *path, char *bname)
(basename)(char *path)
{
const char *endp, *startp;
size_t len;
char *ptr;
/* Empty or NULL string gets treated as "." */
if (path == NULL || *path == '\0') {
bname[0] = '.';
bname[1] = '\0';
return (bname);
}
/*
* If path is a null pointer or points to an empty string,
* basename() shall return a pointer to the string ".".
*/
if (path == NULL || *path == '\0')
return (__DECONST(char *, "."));
/* Strip any trailing slashes */
endp = path + strlen(path) - 1;
while (endp > path && *endp == '/')
endp--;
/* Find end of last pathname component and null terminate it. */
ptr = path + strlen(path);
while (ptr > path + 1 && *(ptr - 1) == '/')
--ptr;
*ptr-- = '\0';
/* All slashes becomes "/" */
if (endp == path && *endp == '/') {
bname[0] = '/';
bname[1] = '\0';
return (bname);
}
/* Find the start of the base */
startp = endp;
while (startp > path && *(startp - 1) != '/')
startp--;
len = endp - startp + 1;
if (len >= MAXPATHLEN) {
errno = ENAMETOOLONG;
return (NULL);
}
memcpy(bname, startp, len);
bname[len] = '\0';
return (bname);
}
char *
basename(char *path)
{
static char *bname = NULL;
if (bname == NULL) {
bname = (char *)malloc(MAXPATHLEN);
if (bname == NULL)
return (NULL);
}
return (basename_r(path, bname));
/* Find beginning of last pathname component. */
while (ptr > path && *(ptr - 1) != '/')
--ptr;
return (ptr);
}

81
lib/libc/gen/basename_compat.c Normal file
View File

@ -0,0 +1,81 @@
/* $OpenBSD: basename.c,v 1.14 2005/08/08 08:05:33 espie Exp $ */
/*
* Copyright (c) 1997, 2004 Todd C. Miller <Todd.Miller@courtesan.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <errno.h>
#include <libgen.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
char *
basename_r(const char *path, char *bname)
{
const char *endp, *startp;
size_t len;
/* Empty or NULL string gets treated as "." */
if (path == NULL || *path == '\0') {
bname[0] = '.';
bname[1] = '\0';
return (bname);
}
/* Strip any trailing slashes */
endp = path + strlen(path) - 1;
while (endp > path && *endp == '/')
endp--;
/* All slashes becomes "/" */
if (endp == path && *endp == '/') {
bname[0] = '/';
bname[1] = '\0';
return (bname);
}
/* Find the start of the base */
startp = endp;
while (startp > path && *(startp - 1) != '/')
startp--;
len = endp - startp + 1;
if (len >= MAXPATHLEN) {
errno = ENAMETOOLONG;
return (NULL);
}
memcpy(bname, startp, len);
bname[len] = '\0';
return (bname);
}
char *
__freebsd11_basename(char *path)
{
static char *bname = NULL;
if (bname == NULL) {
bname = (char *)malloc(MAXPATHLEN);
if (bname == NULL)
return (NULL);
}
return (basename_r(path, bname));
}
__sym_compat(basename, __freebsd11_basename, FBSD_1.0);