/*
* parse the dirs= mount argument
*
* We don't need to lock the superblock private data's rwsem, as we get
* called only by unionfs_read_super - it is still a long time before anyone
* can even get a reference to us.
*/
static int parse_dirs_option(struct super_block *sb, struct unionfs_dentry_info
*lower_root_info, char *options)
{
struct nameidata nd;
char *name;
int err = 0;
int branches = 1;
int bindex = 0;
int i = 0;
int j = 0;
struct dentry *dent1;
struct dentry *dent2;
if (options[0] == '\0') {
printk(KERN_ERR "unionfs: no branches specified\n");
err = -EINVAL;
goto out;
}
/*
* Each colon means we have a separator, this is really just a rough
* guess, since strsep will handle empty fields for us.
*/
for (i = 0; options[i]; i++)
if (options[i] == ':')
branches++;
/* allocate space for underlying pointers to lower dentry */
UNIONFS_SB(sb)->data =
kcalloc(branches, sizeof(struct unionfs_data), GFP_KERNEL);
if (unlikely(!UNIONFS_SB(sb)->data)) {
err = -ENOMEM;
goto out;
}
lower_root_info->lower_paths =
kcalloc(branches, sizeof(struct path), GFP_KERNEL);
if (unlikely(!lower_root_info->lower_paths)) {
err = -ENOMEM;
goto out;
}
/* now parsing a string such as "b1:b2=rw:b3=ro:b4" */
branches = 0;
while ((name = strsep(&options, ":")) != NULL) {
int perms;
char *mode = strchr(name, '=');
if (!name)
continue;
if (!*name) { /* bad use of ':' (extra colons) */
err = -EINVAL;
goto out;
}
branches++;
/* strip off '=' if any */
if (mode)
*mode++ = '\0';
err = parse_branch_mode(mode, &perms);
if (err) {
printk(KERN_ERR "unionfs: invalid mode \"%s\" for "
"branch %d\n", mode, bindex);
goto out;
}
/* ensure that leftmost branch is writeable */
if (!bindex && !(perms & MAY_WRITE)) {
printk(KERN_ERR "unionfs: leftmost branch cannot be "
"read-only (use \"-o ro\" to create a "
"read-only union)\n");
err = -EINVAL;
goto out;
}
err = path_lookup(name, LOOKUP_FOLLOW, &nd);
if (err) {
printk(KERN_ERR "unionfs: error accessing "
"lower directory '%s' (error %d)\n",
name, err);
goto out;
}
err = check_branch(&nd);
if (err) {
printk(KERN_ERR "unionfs: lower directory "
"'%s' is not a valid branch\n", name);
path_release(&nd);
goto out;
}
lower_root_info->lower_paths[bindex].dentry = nd.dentry;
lower_root_info->lower_paths[bindex].mnt = nd.mnt;
set_branchperms(sb, bindex, perms);
set_branch_count(sb, bindex, 0);
new_branch_id(sb, bindex);
if (lower_root_info->bstart < 0)
lower_root_info->bstart = bindex;
lower_root_info->bend = bindex;
bindex++;
}
if (branches == 0) {
printk(KERN_ERR "unionfs: no branches specified\n");
err = -EINVAL;
goto out;
}
BUG_ON(branches != (lower_root_info->bend + 1));
/*
* Ensure that no overlaps exist in the branches.
*
* This test is required because the Linux kernel has no support
* currently for ensuring coherency between stackable layers and
* branches. If we were to allow overlapping branches, it would be
* possible, for example, to delete a file via one branch, which
* would not be reflected in another branch. Such incoherency could
* lead to inconsistencies and even kernel oopses. Rather than
* implement hacks to work around some of these cache-coherency
* problems, we prevent branch overlapping, for now. A complete
* solution will involve proper kernel/VFS support for cache
* coherency, at which time we could safely remove this
* branch-overlapping test.
*/
for (i = 0; i < branches; i++) {
dent1 = lower_root_info->lower_paths[i].dentry;
for (j = i + 1; j < branches; j++) {
dent2 = lower_root_info->lower_paths[j].dentry;
if (is_branch_overlap(dent1, dent2)) {
printk(KERN_ERR "unionfs: branches %d and "
"%d overlap\n", i, j);
err = -EINVAL;
goto out;
}
}
}
out:
if (err) {
for (i = 0; i < branches; i++)
if (lower_root_info->lower_paths[i].dentry) {
dput(lower_root_info->lower_paths[i].dentry);
/* initialize: can't use unionfs_mntput here */
mntput(lower_root_info->lower_paths[i].mnt);
}
kfree(lower_root_info->lower_paths);
kfree(UNIONFS_SB(sb)->data);
/*
* MUST clear the pointers to prevent potential double free if
* the caller dies later on
*/
lower_root_info->lower_paths = NULL;
UNIONFS_SB(sb)->data = NULL;
}
return err;
}
static struct wrapfs_dentry_info *wrapfs_parse_options(struct super_block *sb,
char *options)
{
struct wrapfs_dentry_info *lower_root_info;
struct path path;
struct dentry *dent1, *dent2;
char *optname;
int err = 0, branches = 2;
int dirsfound = 0;
int i = 0;
bool is_ldir_present = false;
bool is_rdir_present = false;
lower_root_info =
kzalloc(sizeof(struct wrapfs_dentry_info), GFP_KERNEL);
if (unlikely(!lower_root_info))
goto out_error;
WRAPFS_SB(sb)->data = kcalloc(branches,
sizeof(struct wrapfs_data), GFP_KERNEL);
if (unlikely(!WRAPFS_SB(sb)->data)) {
err = -ENOMEM;
goto out_return;
}
lower_root_info->lower_paths = kcalloc(branches,
sizeof(struct path), GFP_KERNEL);
if (unlikely(!lower_root_info->lower_paths)) {
err = -ENOMEM;
kfree(WRAPFS_SB(sb)->data);
WRAPFS_SB(sb)->data = NULL;
goto out_return;
}
while ((optname = strsep(&options, ",")) != NULL) {
char *optarg;
if (!optname || !*optname)
continue;
optarg = strchr(optname, '=');
if (optarg)
*optarg++ = '\0';
if (!optarg) {
printk(KERN_ERR "u2fs: %s requires an argument\n",
optname);
err = -EINVAL;
goto out_error;
}
if (!strcmp("ldir", optname)) {
if (++dirsfound > 1) {
printk(KERN_ERR
"u2fs: multiple ldirs specified\n");
err = -EINVAL;
goto out_error;
}
err = kern_path(optarg,
LOOKUP_FOLLOW | LOOKUP_DIRECTORY,
&path);
if (err) {
printk(KERN_ERR "u2fs: error accessing "
"lower directory '%s'\n",
optarg);
goto out_error;
}
err = check_branch(&path);
if (err) {
printk(KERN_ERR "u2fs: lower directory "
"'%s' is not a valid branch\n",
optarg);
path_put(&path);
goto out_error;
}
lower_root_info->lower_paths[0].dentry = path.dentry;
lower_root_info->lower_paths[0].mnt = path.mnt;
WRAPFS_SB(sb)->data[0].branchperms =
MAY_READ|MAY_WRITE;
set_branch_count(sb, 0, 0);
new_branch_id(sb, 0);
is_ldir_present = true;
continue;
}
if (!strcmp("rdir", optname)) {
if (!is_ldir_present)
printk(KERN_ERR "u2fs: ldir not specified\n");
if (++dirsfound > 2) {
printk(KERN_ERR
"u2fs: multiple rdirs specified\n");
err = -EINVAL;
goto out_error;
}
err = kern_path(optarg,
LOOKUP_FOLLOW | LOOKUP_DIRECTORY,
&path);
if (err) {
printk(KERN_ERR "u2fs: error accessing "
"lower directory '%s'\n",
optarg);
goto out_error;
}
lower_root_info->lower_paths[1].dentry = path.dentry;
lower_root_info->lower_paths[1].mnt = path.mnt;
WRAPFS_SB(sb)->data[1].branchperms = MAY_READ;
set_branch_count(sb, 1, 0);
new_branch_id(sb, 1);
is_rdir_present = true;
continue;
}
err = -EINVAL;
printk(KERN_ERR "u2fs: unrecognized options '%s'\n", optname);
goto out_error;
}
if (is_ldir_present && is_rdir_present) {
/* Ensuring no overlaps */
dent1 = lower_root_info->lower_paths[0].dentry;
dent2 = lower_root_info->lower_paths[1].dentry;
if (is_branch_overlap(dent1, dent2)) {
printk(KERN_ERR "u2fs:"
"branches ldir and rdir overlap\n");
err = -EINVAL;
goto out_error;
}
} else {
printk(KERN_ERR "u2fs: no branches specified\n");
err = -EINVAL;
goto out_error;
}
goto out_return;
out_error:
if (lower_root_info && lower_root_info->lower_paths) {
for (i = 0; i < branches; i++)
path_put(&lower_root_info->lower_paths[i]);
kfree(lower_root_info->lower_paths);
kfree(lower_root_info);
kfree(WRAPFS_SB(sb)->data);
lower_root_info->lower_paths = NULL;
WRAPFS_SB(sb)->data = NULL;
lower_root_info = ERR_PTR(err);
}
out_return:
return lower_root_info;
}
