[Libguestfs] [PATCH libguestfs v2 1/3] daemon: xattr: Refactor code which splits attr names from the kernel.
Richard W.M. Jones
rjones at redhat.com
Mon Mar 16 13:59:27 UTC 2020
The kernel returns xattr names in a slightly peculiar format. We
parsed this format several times in the code. Refactor this parsing
so we only do it in one place.
---
daemon/xattr.c | 123 ++++++++++++++++++++++++++++++-------------------
1 file changed, 75 insertions(+), 48 deletions(-)
diff --git a/daemon/xattr.c b/daemon/xattr.c
index 5c9f064ce..761f6074b 100644
--- a/daemon/xattr.c
+++ b/daemon/xattr.c
@@ -89,6 +89,32 @@ do_lremovexattr (const char *xattr, const char *path)
return _removexattr (xattr, path, lremovexattr);
}
+/**
+ * L<listxattr(2)> returns the string C<"foo\0bar\0baz"> of length
+ * C<len>. (The last string in the list is \0-terminated but the \0
+ * is not included in C<len>).
+ *
+ * This function splits it into a regular list of strings.
+ *
+ * B<Note> that the returned list contains pointers to the original
+ * strings in C<buf> so be careful that you do not double-free them.
+ */
+static char **
+split_attr_names (char *buf, size_t len)
+{
+ size_t i;
+ DECLARE_STRINGSBUF (ret);
+
+ for (i = 0; i < len; i += strlen (&buf[i]) + 1) {
+ if (add_string_nodup (&ret, &buf[i]) == -1)
+ return NULL;
+ }
+ if (end_stringsbuf (&ret) == -1)
+ return NULL;
+
+ return take_stringsbuf (&ret);
+}
+
static int
compare_xattrs (const void *vxa1, const void *vxa2)
{
@@ -106,7 +132,8 @@ getxattrs (const char *path,
{
ssize_t len, vlen;
CLEANUP_FREE char *buf = NULL;
- size_t i, j;
+ CLEANUP_FREE /* not string list */ char **names = NULL;
+ size_t i;
guestfs_int_xattr_list *r = NULL;
buf = _listxattrs (path, listxattr, &len);
@@ -114,18 +141,17 @@ getxattrs (const char *path,
/* _listxattrs issues reply_with_perror already. */
goto error;
+ names = split_attr_names (buf, len);
+ if (names == NULL)
+ goto error;
+
r = calloc (1, sizeof (*r));
if (r == NULL) {
reply_with_perror ("calloc");
goto error;
}
- /* What we get from the kernel is a string "foo\0bar\0baz" of length
- * len. First count the strings.
- */
- r->guestfs_int_xattr_list_len = 0;
- for (i = 0; i < (size_t) len; i += strlen (&buf[i]) + 1)
- r->guestfs_int_xattr_list_len++;
+ r->guestfs_int_xattr_list_len = guestfs_int_count_strings (names);
r->guestfs_int_xattr_list_val =
calloc (r->guestfs_int_xattr_list_len, sizeof (guestfs_int_xattr));
@@ -134,34 +160,34 @@ getxattrs (const char *path,
goto error;
}
- for (i = 0, j = 0; i < (size_t) len; i += strlen (&buf[i]) + 1, ++j) {
+ for (i = 0; names[i] != NULL; ++i) {
CHROOT_IN;
- vlen = getxattr (path, &buf[i], NULL, 0);
+ vlen = getxattr (path, names[i], NULL, 0);
CHROOT_OUT;
if (vlen == -1) {
- reply_with_perror ("getxattr");
+ reply_with_perror ("getxattr: %s", names[i]);
goto error;
}
if (vlen > XATTR_SIZE_MAX) {
/* The next call to getxattr will fail anyway, so ... */
- reply_with_error ("extended attribute is too large");
+ reply_with_error ("%s: extended attribute is too large", names[i]);
goto error;
}
- r->guestfs_int_xattr_list_val[j].attrname = strdup (&buf[i]);
- r->guestfs_int_xattr_list_val[j].attrval.attrval_val = malloc (vlen);
- r->guestfs_int_xattr_list_val[j].attrval.attrval_len = vlen;
+ r->guestfs_int_xattr_list_val[i].attrname = strdup (names[i]);
+ r->guestfs_int_xattr_list_val[i].attrval.attrval_val = malloc (vlen);
+ r->guestfs_int_xattr_list_val[i].attrval.attrval_len = vlen;
- if (r->guestfs_int_xattr_list_val[j].attrname == NULL ||
- r->guestfs_int_xattr_list_val[j].attrval.attrval_val == NULL) {
+ if (r->guestfs_int_xattr_list_val[i].attrname == NULL ||
+ r->guestfs_int_xattr_list_val[i].attrval.attrval_val == NULL) {
reply_with_perror ("malloc");
goto error;
}
CHROOT_IN;
- vlen = getxattr (path, &buf[i],
- r->guestfs_int_xattr_list_val[j].attrval.attrval_val,
+ vlen = getxattr (path, names[i],
+ r->guestfs_int_xattr_list_val[i].attrval.attrval_val,
vlen);
CHROOT_OUT;
if (vlen == -1) {
@@ -276,7 +302,7 @@ guestfs_int_xattr_list *
do_internal_lxattrlist (const char *path, char *const *names)
{
guestfs_int_xattr_list *ret = NULL;
- size_t i, j;
+ size_t i;
size_t k, m, nr_attrs;
ssize_t len, vlen;
@@ -293,6 +319,7 @@ do_internal_lxattrlist (const char *path, char *const *names)
void *newptr;
CLEANUP_FREE char *pathname = NULL;
CLEANUP_FREE char *buf = NULL;
+ CLEANUP_FREE /* not string list */ char **attrnames = NULL;
/* Be careful in this loop about which errors cause the whole call
* to abort, and which errors allow us to continue processing
@@ -350,12 +377,10 @@ do_internal_lxattrlist (const char *path, char *const *names)
if (len == -1)
continue; /* not fatal */
- /* What we get from the kernel is a string "foo\0bar\0baz" of length
- * len. First count the strings.
- */
- nr_attrs = 0;
- for (i = 0; i < (size_t) len; i += strlen (&buf[i]) + 1)
- nr_attrs++;
+ attrnames = split_attr_names (buf, len);
+ if (attrnames == NULL)
+ goto error;
+ nr_attrs = guestfs_int_count_strings (attrnames);
newptr =
realloc (ret->guestfs_int_xattr_list_val,
@@ -378,36 +403,36 @@ do_internal_lxattrlist (const char *path, char *const *names)
entry[m].attrval.attrval_val = NULL;
}
- for (i = 0, j = 0; i < (size_t) len; i += strlen (&buf[i]) + 1, ++j) {
+ for (i = 0; attrnames[i] != NULL; ++i) {
CHROOT_IN;
- vlen = lgetxattr (pathname, &buf[i], NULL, 0);
+ vlen = lgetxattr (pathname, attrnames[i], NULL, 0);
CHROOT_OUT;
if (vlen == -1) {
- reply_with_perror ("getxattr");
+ reply_with_perror ("getxattr: %s", attrnames[i]);
goto error;
}
if (vlen > XATTR_SIZE_MAX) {
- reply_with_error ("extended attribute is too large");
+ reply_with_error ("%s: extended attribute is too large", attrnames[i]);
goto error;
}
- entry[j+1].attrname = strdup (&buf[i]);
- entry[j+1].attrval.attrval_val = malloc (vlen);
- entry[j+1].attrval.attrval_len = vlen;
+ entry[i+1].attrname = strdup (attrnames[i]);
+ entry[i+1].attrval.attrval_val = malloc (vlen);
+ entry[i+1].attrval.attrval_len = vlen;
- if (entry[j+1].attrname == NULL ||
- entry[j+1].attrval.attrval_val == NULL) {
+ if (entry[i+1].attrname == NULL ||
+ entry[i+1].attrval.attrval_val == NULL) {
reply_with_perror ("malloc");
goto error;
}
CHROOT_IN;
- vlen = lgetxattr (pathname, &buf[i],
- entry[j+1].attrval.attrval_val, vlen);
+ vlen = lgetxattr (pathname, attrnames[i],
+ entry[i+1].attrval.attrval_val, vlen);
CHROOT_OUT;
if (vlen == -1) {
- reply_with_perror ("getxattr");
+ reply_with_perror ("getxattr: %s", attrnames[i]);
goto error;
}
}
@@ -510,6 +535,7 @@ copy_xattrs (const char *src, const char *dest)
{
ssize_t len, vlen, ret, attrval_len = 0;
CLEANUP_FREE char *buf = NULL, *attrval = NULL;
+ CLEANUP_FREE /* not string list */ char **names = NULL;
size_t i;
buf = _listxattrs (src, listxattr, &len);
@@ -517,21 +543,22 @@ copy_xattrs (const char *src, const char *dest)
/* _listxattrs issues reply_with_perror already. */
goto error;
- /* What we get from the kernel is a string "foo\0bar\0baz" of length
- * len.
- */
- for (i = 0; i < (size_t) len; i += strlen (&buf[i]) + 1) {
+ names = split_attr_names (buf, len);
+ if (names == NULL)
+ goto error;
+
+ for (i = 0; names[i] != NULL; ++i) {
CHROOT_IN;
- vlen = getxattr (src, &buf[i], NULL, 0);
+ vlen = getxattr (src, names[i], NULL, 0);
CHROOT_OUT;
if (vlen == -1) {
- reply_with_perror ("getxattr: %s, %s", src, &buf[i]);
+ reply_with_perror ("getxattr: %s, %s", src, names[i]);
goto error;
}
if (vlen > XATTR_SIZE_MAX) {
/* The next call to getxattr will fail anyway, so ... */
- reply_with_error ("extended attribute is too large");
+ reply_with_error ("%s: extended attribute is too large", names[i]);
goto error;
}
@@ -546,18 +573,18 @@ copy_xattrs (const char *src, const char *dest)
}
CHROOT_IN;
- vlen = getxattr (src, &buf[i], attrval, vlen);
+ vlen = getxattr (src, names[i], attrval, vlen);
CHROOT_OUT;
if (vlen == -1) {
- reply_with_perror ("getxattr: %s, %s", src, &buf[i]);
+ reply_with_perror ("getxattr: %s, %s", src, names[i]);
goto error;
}
CHROOT_IN;
- ret = setxattr (dest, &buf[i], attrval, vlen, 0);
+ ret = setxattr (dest, names[i], attrval, vlen, 0);
CHROOT_OUT;
if (ret == -1) {
- reply_with_perror ("setxattr: %s, %s", dest, &buf[i]);
+ reply_with_perror ("setxattr: %s, %s", dest, names[i]);
goto error;
}
}
--
2.25.0
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