diff options
| -rw-r--r-- | ChangeLog | 22 | ||||
| -rw-r--r-- | lib/file-has-acl.c | 94 | ||||
| -rw-r--r-- | m4/acl.m4 | 46 |
3 files changed, 105 insertions, 57 deletions
@@ -1,3 +1,25 @@ +2023-05-12 Paul Eggert <eggert@cs.ucla.edu> + + file-has-acl: port to Fedora 39 + Fedora 39 getxattr with XATTR_NAME_POSIX_ACL_ACCESS either + succeeds or fails with ENODATA, so it is no longer possible to + detect from its failure that the filesystem might support NFSv4 ACLs. + Problem reported by Ondrej Valousek in: + https://lists.gnu.org/r/bug-gnulib/2023-04/msg00228.html + Instead, use listxattr to determine whether NFSv4 ACLs are in play. + This typically saves syscalls anyway. + * lib/file-has-acl.c: In #if, use (HAVE_LINUX_XATTR_H && + HAVE_LISTXATTR) instead of GETXATTR_WITH_POSIX_ACLS. + The following changes apply when (USE_ACL && HAVE_LINUX_XATTR_H && + HAVE_LISTXATTR): + Include minmax.h. + (have_xattr): New function. + (file_has_acl): Try listxattr first; typically this means we need + to do no other syscall. Call getxattr only if there are NFSv4 + ACLs but not POSIX ACLs. + * m4/acl.m4 (gl_FILE_HAS_ACL): Simplify by merely testing for + linux/xattr.h and listxattr. All uses changed. + 2023-05-10 Josh Soref <jsoref@gmail.com> bootstrap: spelling/grammar fix in comment diff --git a/lib/file-has-acl.c b/lib/file-has-acl.c index b31a2ea252..1edcd2cbd6 100644 --- a/lib/file-has-acl.c +++ b/lib/file-has-acl.c @@ -29,7 +29,7 @@ #include "acl-internal.h" -#if USE_ACL && GETXATTR_WITH_POSIX_ACLS +#if USE_ACL && HAVE_LINUX_XATTR_H && HAVE_LISTXATTR # include <string.h> # include <arpa/inet.h> # include <sys/xattr.h> @@ -44,6 +44,20 @@ enum { ACE4_IDENTIFIER_GROUP = 0x00000040 }; +/* Return true if ATTR is in the set represented by the NUL-terminated + strings in LISTBUF, which is of size LISTSIZE. */ + +static bool +have_xattr (char const *attr, char const *listbuf, ssize_t listsize) +{ + char const *blim = listbuf + listsize; + for (char const *b = listbuf; b < blim; b += strlen (b) + 1) + for (char const *a = attr; *a == *b; a++, b++) + if (!*a) + return true; + return false; +} + /* Return 1 if given ACL in XDR format is non-trivial, 0 if it is trivial. -1 upon failure to determine it. Possibly change errno. Assume that the ACL is valid, except avoid undefined behavior even if invalid. @@ -137,37 +151,63 @@ file_has_acl (char const *name, struct stat const *sb) if (! S_ISLNK (sb->st_mode)) { -# if GETXATTR_WITH_POSIX_ACLS - - ssize_t ret; +# if HAVE_LINUX_XATTR_H && HAVE_LISTXATTR int initial_errno = errno; - ret = getxattr (name, XATTR_NAME_POSIX_ACL_ACCESS, NULL, 0); - if (ret < 0 && errno == ENODATA) - ret = 0; - else if (ret > 0) - return 1; - - if (ret == 0 && S_ISDIR (sb->st_mode)) + /* The max length of a trivial NFSv4 ACL is 6 words for owner, + 6 for group, 7 for everyone, all times 2 because there are + both allow and deny ACEs. There are 6 words for owner + because of type, flag, mask, wholen, "OWNER@"+pad and + similarly for group; everyone is another word to hold + "EVERYONE@". */ + typedef uint32_t trivial_NFSv4_xattr_buf[2 * (6 + 6 + 7)]; + + /* A buffer large enough to hold any trivial NFSv4 ACL, + and also useful as a small array of char. */ + union { + trivial_NFSv4_xattr_buf xattr; + char ch[sizeof (trivial_NFSv4_xattr_buf)]; + } stackbuf; + + char *listbuf = stackbuf.ch; + ssize_t listbufsize = sizeof stackbuf.ch; + char *heapbuf = NULL; + ssize_t listsize; + + /* Use listxattr first, as this means just one syscall in the + typical case where the file lacks an ACL. Try stackbuf + first, falling back on malloc if stackbuf is too small. */ + while ((listsize = listxattr (name, listbuf, listbufsize)) < 0 + && errno == ERANGE) { - ret = getxattr (name, XATTR_NAME_POSIX_ACL_DEFAULT, NULL, 0); - if (ret < 0 && errno == ENODATA) - ret = 0; - else if (ret > 0) - return 1; + free (heapbuf); + listbufsize = listxattr (name, NULL, 0); + if (listbufsize < 0) + return -1; + if (SIZE_MAX < listbufsize) + { + errno = ENOMEM; + return -1; + } + listbuf = heapbuf = malloc (listbufsize); + if (!listbuf) + return -1; } - if (ret < 0) + int ret + = (listsize < 0 ? -1 + : (have_xattr (XATTR_NAME_POSIX_ACL_ACCESS, listbuf, listsize) + || (S_ISDIR (sb->st_mode) + && have_xattr (XATTR_NAME_POSIX_ACL_DEFAULT, + listbuf, listsize)))); + free (heapbuf); + + /* If there is an NFSv4 ACL but no POSIX ACL, follow up with a + getxattr syscall to see whether the NFSv4 ACL is nontrivial. */ + if (ret == 0 && have_xattr (XATTR_NAME_NFSV4_ACL, listbuf, listsize)) { - /* Check for NFSv4 ACLs. The max length of a trivial - ACL is 6 words for owner, 6 for group, 7 for everyone, - all times 2 because there are both allow and deny ACEs. - There are 6 words for owner because of type, flag, mask, - wholen, "OWNER@"+pad and similarly for group; everyone is - another word to hold "EVERYONE@". */ - uint32_t xattr[2 * (6 + 6 + 7)]; - - ret = getxattr (name, XATTR_NAME_NFSV4_ACL, xattr, sizeof xattr); + ret = getxattr (name, XATTR_NAME_NFSV4_ACL, + stackbuf.xattr, sizeof stackbuf.xattr); if (ret < 0) switch (errno) { @@ -177,7 +217,7 @@ file_has_acl (char const *name, struct stat const *sb) else { /* It looks like a trivial ACL, but investigate further. */ - ret = acl_nfs4_nontrivial (xattr, ret); + ret = acl_nfs4_nontrivial (stackbuf.xattr, ret); if (ret < 0) { errno = EINVAL; @@ -1,5 +1,5 @@ # acl.m4 - check for access control list (ACL) primitives -# serial 28 +# serial 29 # Copyright (C) 2002, 2004-2023 Free Software Foundation, Inc. # This file is free software; the Free Software Foundation @@ -177,37 +177,23 @@ AC_DEFUN([gl_ACL_GET_FILE], AS_IF([test "$gl_cv_func_working_acl_get_file" != no], [$1], [$2]) ]) -# On GNU/Linux, testing if a file has an acl can be done with the getxattr -# syscall which doesn't require linking against additional libraries. +# On GNU/Linux, testing if a file has an acl can be done with the +# listxattr and getxattr syscalls, which don't require linking +# against additional libraries. Assume this works if linux/attr.h +# and listxattr are present. AC_DEFUN([gl_FILE_HAS_ACL], [ AC_REQUIRE([gl_FUNC_ACL_ARG]) - if test "$enable_acl" != no; then - AC_CACHE_CHECK([for getxattr with XATTR_NAME_POSIX_ACL macros], - [gl_cv_getxattr_with_posix_acls], - [gl_cv_getxattr_with_posix_acls=no - AC_LINK_IFELSE( - [AC_LANG_PROGRAM( - [[#include <sys/types.h> - #include <sys/xattr.h> - #include <linux/xattr.h> - ]], - [[ssize_t a = getxattr (".", XATTR_NAME_POSIX_ACL_ACCESS, 0, 0); - ssize_t b = getxattr (".", XATTR_NAME_POSIX_ACL_DEFAULT, 0, 0); - return a < 0 || b < 0; - ]])], - [gl_cv_getxattr_with_posix_acls=yes])]) - fi - if test "$gl_cv_getxattr_with_posix_acls" = yes; then - FILE_HAS_ACL_LIB= - AC_DEFINE([GETXATTR_WITH_POSIX_ACLS], 1, - [Define to 1 if getxattr works with XATTR_NAME_POSIX_ACL_ACCESS - and XATTR_NAME_POSIX_ACL_DEFAULT.]) - else - dnl Set gl_need_lib_has_acl to a nonempty value, so that any - dnl later gl_FUNC_ACL call will set FILE_HAS_ACL_LIB=$LIB_ACL. - gl_need_lib_has_acl=1 - FILE_HAS_ACL_LIB=$LIB_ACL - fi + AC_CHECK_HEADERS_ONCE([linux/xattr.h]) + AC_CHECK_FUNCS_ONCE([listxattr]) + FILE_HAS_ACL_LIB= + AS_CASE([$enable_acl,$ac_cv_header_linux_xattr_h,$ac_cv_func_listxattr], + [no,*,*], [], + [*,yes,yes], [], + [*], + [dnl Set gl_need_lib_has_acl to a nonempty value, so that any + dnl later gl_FUNC_ACL call will set FILE_HAS_ACL_LIB=$LIB_ACL. + gl_need_lib_has_acl=1 + FILE_HAS_ACL_LIB=$LIB_ACL]) AC_SUBST([FILE_HAS_ACL_LIB]) ]) |