diff options
Diffstat (limited to 'lib/file-has-acl.c')
| -rw-r--r-- | lib/file-has-acl.c | 94 |
1 files changed, 67 insertions, 27 deletions
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; |