aboutsummaryrefslogtreecommitdiffstats
path: root/fs/proc/proc_sysctl.c
diff options
context:
space:
mode:
authorEric W. Biederman <ebiederm@xmission.com>2012-01-22 18:22:05 -0800
committerEric W. Biederman <ebiederm@xmission.com>2012-01-24 16:40:27 -0800
commitf728019bb72e655680c02ad1829323054a8e875f (patch)
treecc1915e06b806004c662abb0f0cb4f897111be1c /fs/proc/proc_sysctl.c
parentec6a52668d0bbc6d648e978c327150254bf1ce7f (diff)
sysctl: register only tables of sysctl files
Split the registration of a complex ctl_table array which may have arbitrary numbers of directories (->child != NULL) and tables of files into a series of simpler registrations that only register tables of files. Graphically: register('dir', { + file-a + file-b + subdir1 + file-c + subdir2 + file-d + file-e }) is transformed into: wrapper->subheaders[0] = register('dir', {file1-a, file1-b}) wrapper->subheaders[1] = register('dir/subdir1', {file-c}) wrapper->subheaders[2] = register('dir/subdir2', {file-d, file-e}) return wrapper This guarantees that __register_sysctl_table will only see a simple ctl_table array with all entries having (->child == NULL). Care was taken to pass the original simple ctl_table arrays to __register_sysctl_table whenever possible. This change is derived from a similar patch written by Lucrian Grijincu. Inspired-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Diffstat (limited to 'fs/proc/proc_sysctl.c')
-rw-r--r--fs/proc/proc_sysctl.c165
1 files changed, 147 insertions, 18 deletions
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 9b91deeeb56..6bab2ae9e39 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -882,7 +882,7 @@ static int sysctl_check_table(struct nsproxy *namespaces, struct ctl_table *tabl
#endif /* CONFIG_SYSCTL_SYSCALL_CHECK */
/**
- * __register_sysctl_table - register a sysctl table
+ * __register_sysctl_table - register a leaf sysctl table
* @root: List of sysctl headers to register on
* @namespaces: Data to compute which lists of sysctl entries are visible
* @path: The path to the directory the sysctl table is in.
@@ -900,29 +900,19 @@ static int sysctl_check_table(struct nsproxy *namespaces, struct ctl_table *tabl
*
* maxlen - the maximum size in bytes of the data
*
- * mode - the file permissions for the /proc/sys file, and for sysctl(2)
+ * mode - the file permissions for the /proc/sys file
*
- * child - a pointer to the child sysctl table if this entry is a directory, or
- * %NULL.
+ * child - must be %NULL.
*
* proc_handler - the text handler routine (described below)
*
- * de - for internal use by the sysctl routines
- *
* extra1, extra2 - extra pointers usable by the proc handler routines
*
* Leaf nodes in the sysctl tree will be represented by a single file
* under /proc; non-leaf nodes will be represented by directories.
*
- * sysctl(2) can automatically manage read and write requests through
- * the sysctl table. The data and maxlen fields of the ctl_table
- * struct enable minimal validation of the values being written to be
- * performed, and the mode field allows minimal authentication.
- *
- * There must be a proc_handler routine for any terminal nodes
- * mirrored under /proc/sys (non-terminals are handled by a built-in
- * directory handler). Several default handlers are available to
- * cover common cases -
+ * There must be a proc_handler routine for any terminal nodes.
+ * Several default handlers are available to cover common cases -
*
* proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
* proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
@@ -1059,6 +1049,100 @@ static char *append_path(const char *path, char *pos, const char *name)
return pos;
}
+static int count_subheaders(struct ctl_table *table)
+{
+ int has_files = 0;
+ int nr_subheaders = 0;
+ struct ctl_table *entry;
+
+ /* special case: no directory and empty directory */
+ if (!table || !table->procname)
+ return 1;
+
+ for (entry = table; entry->procname; entry++) {
+ if (entry->child)
+ nr_subheaders += count_subheaders(entry->child);
+ else
+ has_files = 1;
+ }
+ return nr_subheaders + has_files;
+}
+
+static int register_leaf_sysctl_tables(const char *path, char *pos,
+ struct ctl_table_header ***subheader,
+ struct ctl_table_root *root, struct nsproxy *namespaces,
+ struct ctl_table *table)
+{
+ struct ctl_table *ctl_table_arg = NULL;
+ struct ctl_table *entry, *files;
+ int nr_files = 0;
+ int nr_dirs = 0;
+ int err = -ENOMEM;
+
+ for (entry = table; entry->procname; entry++) {
+ if (entry->child)
+ nr_dirs++;
+ else
+ nr_files++;
+ }
+
+ files = table;
+ /* If there are mixed files and directories we need a new table */
+ if (nr_dirs && nr_files) {
+ struct ctl_table *new;
+ files = kzalloc(sizeof(struct ctl_table) * (nr_files + 1),
+ GFP_KERNEL);
+ if (!files)
+ goto out;
+
+ ctl_table_arg = files;
+ for (new = files, entry = table; entry->procname; entry++) {
+ if (entry->child)
+ continue;
+ *new = *entry;
+ new++;
+ }
+ }
+
+ /* Register everything except a directory full of subdirectories */
+ if (nr_files || !nr_dirs) {
+ struct ctl_table_header *header;
+ header = __register_sysctl_table(root, namespaces, path, files);
+ if (!header) {
+ kfree(ctl_table_arg);
+ goto out;
+ }
+
+ /* Remember if we need to free the file table */
+ header->ctl_table_arg = ctl_table_arg;
+ **subheader = header;
+ (*subheader)++;
+ }
+
+ /* Recurse into the subdirectories. */
+ for (entry = table; entry->procname; entry++) {
+ char *child_pos;
+
+ if (!entry->child)
+ continue;
+
+ err = -ENAMETOOLONG;
+ child_pos = append_path(path, pos, entry->procname);
+ if (!child_pos)
+ goto out;
+
+ err = register_leaf_sysctl_tables(path, child_pos, subheader,
+ root, namespaces, entry->child);
+ pos[0] = '\0';
+ if (err)
+ goto out;
+ }
+ err = 0;
+out:
+ /* On failure our caller will unregister all registered subheaders */
+ return err;
+}
+
/**
* __register_sysctl_paths - register a sysctl table hierarchy
* @root: List of sysctl headers to register on
@@ -1077,7 +1161,8 @@ struct ctl_table_header *__register_sysctl_paths(
const struct ctl_path *path, struct ctl_table *table)
{
struct ctl_table *ctl_table_arg = table;
- struct ctl_table_header *header = NULL;
+ int nr_subheaders = count_subheaders(table);
+ struct ctl_table_header *header = NULL, **subheaders, **subheader;
const struct ctl_path *component;
char *new_path, *pos;
@@ -1097,12 +1182,39 @@ struct ctl_table_header *__register_sysctl_paths(
goto out;
table = table->child;
}
- header = __register_sysctl_table(root, namespaces, new_path, table);
- if (header)
+ if (nr_subheaders == 1) {
+ header = __register_sysctl_table(root, namespaces, new_path, table);
+ if (header)
+ header->ctl_table_arg = ctl_table_arg;
+ } else {
+ header = kzalloc(sizeof(*header) +
+ sizeof(*subheaders)*nr_subheaders, GFP_KERNEL);
+ if (!header)
+ goto out;
+
+ subheaders = (struct ctl_table_header **) (header + 1);
+ subheader = subheaders;
header->ctl_table_arg = ctl_table_arg;
+
+ if (register_leaf_sysctl_tables(new_path, pos, &subheader,
+ root, namespaces, table))
+ goto err_register_leaves;
+ }
+
out:
kfree(new_path);
return header;
+
+err_register_leaves:
+ while (subheader > subheaders) {
+ struct ctl_table_header *subh = *(--subheader);
+ struct ctl_table *table = subh->ctl_table_arg;
+ unregister_sysctl_table(subh);
+ kfree(table);
+ }
+ kfree(header);
+ header = NULL;
+ goto out;
}
/**
@@ -1149,11 +1261,28 @@ EXPORT_SYMBOL(register_sysctl_table);
*/
void unregister_sysctl_table(struct ctl_table_header * header)
{
+ int nr_subheaders;
might_sleep();
if (header == NULL)
return;
+ nr_subheaders = count_subheaders(header->ctl_table_arg);
+ if (unlikely(nr_subheaders > 1)) {
+ struct ctl_table_header **subheaders;
+ int i;
+
+ subheaders = (struct ctl_table_header **)(header + 1);
+ for (i = nr_subheaders -1; i >= 0; i--) {
+ struct ctl_table_header *subh = subheaders[i];
+ struct ctl_table *table = subh->ctl_table_arg;
+ unregister_sysctl_table(subh);
+ kfree(table);
+ }
+ kfree(header);
+ return;
+ }
+
spin_lock(&sysctl_lock);
start_unregistering(header);
if (!--header->parent->count) {