From 09e1178b5bd61bf1bf946469cea8cb4c54f923db Mon Sep 17 00:00:00 2001 From: ed Date: Fri, 12 Aug 2016 07:03:58 +0000 Subject: [PATCH] Reimplement dirname(3) to be thread-safe. Now that we've updated the prototypes of the basename(3) and dirname(3) functions to conform to POSIX, let's go ahead and reimplement dirname(3) in such a way that it's thread-safe, but also guaranteed to succeed. C libraries like glibc, musl and the one that's part of Solaris already follow such an approach. Move the existing implementation to another source file, freebsd11_dirname.c to keep existing users of the API that pass in a constant string happy, using symbol versioning. Put a new version of the function in dirname.c, obtained from CloudABI's C library. This version scans through the pathname string from left to right, normalizing it, while discarding the last pathname component. Reviewed by: emaste, jilles Differential Revision: https://reviews.freebsd.org/D7355 --- lib/libc/gen/Makefile.inc | 1 + lib/libc/gen/Symbol.map | 5 +- lib/libc/gen/dirname.3 | 58 ++++++--------- lib/libc/gen/dirname.c | 133 +++++++++++++++++++--------------- lib/libc/gen/dirname_compat.c | 79 ++++++++++++++++++++ 5 files changed, 181 insertions(+), 95 deletions(-) create mode 100644 lib/libc/gen/dirname_compat.c diff --git a/lib/libc/gen/Makefile.inc b/lib/libc/gen/Makefile.inc index 696d907ac609..58f582fb4e73 100644 --- a/lib/libc/gen/Makefile.inc +++ b/lib/libc/gen/Makefile.inc @@ -29,6 +29,7 @@ SRCS+= __getosreldate.c \ devname.c \ dirfd.c \ dirname.c \ + dirname_compat.c \ disklabel.c \ dlfcn.c \ drand48.c \ diff --git a/lib/libc/gen/Symbol.map b/lib/libc/gen/Symbol.map index 0d5dfec80cce..6e5db3d8abb6 100644 --- a/lib/libc/gen/Symbol.map +++ b/lib/libc/gen/Symbol.map @@ -82,7 +82,6 @@ FBSD_1.0 { daemon; devname; devname_r; - dirname; getdiskbyname; dladdr; dlclose; @@ -418,6 +417,10 @@ FBSD_1.4 { stravis; }; +FBSD_1.5 { + dirname; +}; + FBSDprivate_1.0 { /* needed by thread libraries */ __thr_jtable; diff --git a/lib/libc/gen/dirname.3 b/lib/libc/gen/dirname.3 index 6685618a9869..18405f9af6ef 100644 --- a/lib/libc/gen/dirname.3 +++ b/lib/libc/gen/dirname.3 @@ -16,7 +16,7 @@ .\" .\" $FreeBSD$ .\" -.Dd July 29, 2016 +.Dd August 12, 2016 .Dt DIRNAME 3 .Os .Sh NAME @@ -37,6 +37,7 @@ Any trailing .Sq \&/ characters are not counted as part of the directory name. +.Sh RETURN VALUES If .Fa path is a null pointer, the empty string, or contains no @@ -46,40 +47,24 @@ characters, returns a pointer to the string .Qq \&. , signifying the current directory. -.Sh IMPLEMENTATION NOTES -The -.Fn dirname -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 dirname -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. -.Sh RETURN VALUES -On successful completion, -.Fn dirname -returns a pointer to the parent directory of +Otherwise, +it returns a pointer to the parent directory of .Fa path . -.Pp -If +.Sh IMPLEMENTATION NOTES +This implementation of .Fn dirname -fails, 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 +uses the buffer provided by the caller to store the resulting parent +directory. +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. +.Pp +The algorithm used by this implementation also discards redundant +slashes and +.Qq \&. +pathname components from the pathname string. .Sh SEE ALSO .Xr basename 1 , .Xr dirname 1 , @@ -96,5 +81,10 @@ function first appeared in .Ox 2.2 and .Fx 4.2 . +.Pp +In +.Fx 12.0 , +this function was reimplemented to store its result in the provided +input buffer. .Sh AUTHORS -.An "Todd C. Miller" +.An Nuxi, the Netherlands diff --git a/lib/libc/gen/dirname.c b/lib/libc/gen/dirname.c index 5e0042fd2d10..3113631ac943 100644 --- a/lib/libc/gen/dirname.c +++ b/lib/libc/gen/dirname.c @@ -1,77 +1,90 @@ -/* $OpenBSD: dirname.c,v 1.13 2005/08/08 08:05:33 espie Exp $ */ - -/* - * Copyright (c) 1997, 2004 Todd C. Miller +/*- + * 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 __FBSDID("$FreeBSD$"); -#include #include -#include +#include #include -#include char * dirname(char *path) { - static char *dname = NULL; - size_t len; - const char *endp; + const char *in, *prev, *begin, *end; + char *out; + size_t prevlen; + bool skipslash; - if (dname == NULL) { - dname = (char *)malloc(MAXPATHLEN); - if (dname == NULL) - return(NULL); + /* + * If path is a null pointer or points to an empty string, + * dirname() shall return a pointer to the string ".". + */ + if (path == NULL || *path == '\0') + return ((char *)"."); + + /* Retain at least one leading slash character. */ + in = out = *path == '/' ? path + 1 : path; + + skipslash = true; + prev = "."; + prevlen = 1; + for (;;) { + /* Extract the next pathname component. */ + while (*in == '/') + ++in; + begin = in; + while (*in != '/' && *in != '\0') + ++in; + end = in; + if (begin == end) + break; + + /* + * Copy over the previous pathname component, except if + * it's dot. There is no point in retaining those. + */ + if (prevlen != 1 || *prev != '.') { + if (!skipslash) + *out++ = '/'; + skipslash = false; + memmove(out, prev, prevlen); + out += prevlen; + } + + /* Preserve the pathname component for the next iteration. */ + prev = begin; + prevlen = end - begin; } - /* Empty or NULL string gets treated as "." */ - if (path == NULL || *path == '\0') { - dname[0] = '.'; - dname[1] = '\0'; - return (dname); - } - - /* Strip any trailing slashes */ - endp = path + strlen(path) - 1; - while (endp > path && *endp == '/') - endp--; - - /* Find the start of the dir */ - while (endp > path && *endp != '/') - endp--; - - /* Either the dir is "/" or there are no slashes */ - if (endp == path) { - dname[0] = *endp == '/' ? '/' : '.'; - dname[1] = '\0'; - return (dname); - } else { - /* Move forward past the separating slashes */ - do { - endp--; - } while (endp > path && *endp == '/'); - } - - len = endp - path + 1; - if (len >= MAXPATHLEN) { - errno = ENAMETOOLONG; - return (NULL); - } - memcpy(dname, path, len); - dname[len] = '\0'; - return (dname); + /* + * If path does not contain a '/', then dirname() shall return a + * pointer to the string ".". + */ + if (out == path) + *out++ = '.'; + *out = '\0'; + return (path); } diff --git a/lib/libc/gen/dirname_compat.c b/lib/libc/gen/dirname_compat.c new file mode 100644 index 000000000000..48ad32c8d70a --- /dev/null +++ b/lib/libc/gen/dirname_compat.c @@ -0,0 +1,79 @@ +/* $OpenBSD: dirname.c,v 1.13 2005/08/08 08:05:33 espie Exp $ */ + +/* + * Copyright (c) 1997, 2004 Todd C. Miller + * + * 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 +__FBSDID("$FreeBSD$"); + +#include +#include +#include +#include +#include + +char * +__freebsd11_dirname(char *path) +{ + static char *dname = NULL; + size_t len; + const char *endp; + + if (dname == NULL) { + dname = (char *)malloc(MAXPATHLEN); + if (dname == NULL) + return(NULL); + } + + /* Empty or NULL string gets treated as "." */ + if (path == NULL || *path == '\0') { + dname[0] = '.'; + dname[1] = '\0'; + return (dname); + } + + /* Strip any trailing slashes */ + endp = path + strlen(path) - 1; + while (endp > path && *endp == '/') + endp--; + + /* Find the start of the dir */ + while (endp > path && *endp != '/') + endp--; + + /* Either the dir is "/" or there are no slashes */ + if (endp == path) { + dname[0] = *endp == '/' ? '/' : '.'; + dname[1] = '\0'; + return (dname); + } else { + /* Move forward past the separating slashes */ + do { + endp--; + } while (endp > path && *endp == '/'); + } + + len = endp - path + 1; + if (len >= MAXPATHLEN) { + errno = ENAMETOOLONG; + return (NULL); + } + memcpy(dname, path, len); + dname[len] = '\0'; + return (dname); +} + +__sym_compat(dirname, __freebsd11_dirname, FBSD_1.0);