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sysctl: Improve the sysctl sanity checks 

- Stop validating subdirectories now that we only register leaf tables

- Cleanup and improve the duplicate filename check.
  * Run the duplicate filename check under the sysctl_lock to guarantee
    we never add duplicate names.
  * Reduce the duplicate filename check to nearly O(M*N) where M is the
    number of entries in tthe table we are registering and N is the
    number of entries in the directory before we got there.

- Move the duplicate filename check into it's own function and call
  it directtly from __register_sysctl_table

- Kill the config option as the sanity checks are now cheap enough
  the config option is unnecessary. The original reason for the config
  option was because we had a huge table used to verify the proc filename
  to binary sysctl mapping.  That table has now evolved into the binary_sysctl
  translation layer and is no longer part of the sysctl_check code.

- Tighten up the permission checks.  Guarnateeing that files only have read
  or write permissions.

- Removed redudant check for parents having a procname as now everything has
  a procname.

- Generalize the backtrace logic so that we print a backtrace from
  any failure of __register_sysctl_table that was not caused by
  a memmory allocation failure.  The backtrace allows us to track
  down who erroneously registered a sysctl table.

Bechmark before (CONFIG_SYSCTL_CHECK=y):
    make-dummies 0 999 -> 12s
    rmmod dummy        -> 0.08s

Bechmark before (CONFIG_SYSCTL_CHECK=n):
    make-dummies 0 999 -> 0.7s
    rmmod dummy        -> 0.06s
    make-dummies 0 99999 -> 1m13s
    rmmod dummy          -> 0.38s

Benchmark after:
    make-dummies 0 999 -> 0.65s
    rmmod dummy        -> 0.055s
    make-dummies 0 9999 -> 1m10s
    rmmod dummy         -> 0.39s

The sysctl sanity checks now impose no measurable cost.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2012-01-21 13:34:05 -08:00
parent f728019bb7
commit 7c60c48f58
2 changed files with 102 additions and 160 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

254
fs/proc/proc_sysctl.c
View File

@ -726,160 +726,106 @@ static void try_attach(struct ctl_table_header *p, struct ctl_table_header *q)
}
}
#ifdef CONFIG_SYSCTL_SYSCALL_CHECK
static int sysctl_depth(struct ctl_table *table)
{
struct ctl_table *tmp;
int depth;
depth = 0;
for (tmp = table; tmp->parent; tmp = tmp->parent)
depth++;
return depth;
}
static struct ctl_table *sysctl_parent(struct ctl_table *table, int n)
{
int i;
for (i = 0; table && i < n; i++)
table = table->parent;
return table;
}
static void sysctl_print_path(struct ctl_table *table)
{
struct ctl_table *tmp;
int depth, i;
depth = sysctl_depth(table);
if (table->procname) {
for (i = depth; i >= 0; i--) {
tmp = sysctl_parent(table, i);
printk("/%s", tmp->procname?tmp->procname:"");
}
}
printk(" ");
}
static struct ctl_table *sysctl_check_lookup(struct nsproxy *namespaces,
struct ctl_table *table)
{
struct ctl_table_header *head;
struct ctl_table *ref, *test;
int depth, cur_depth;
depth = sysctl_depth(table);
for (head = __sysctl_head_next(namespaces, NULL); head;
head = __sysctl_head_next(namespaces, head)) {
cur_depth = depth;
ref = head->ctl_table;
repeat:
test = sysctl_parent(table, cur_depth);
for (; ref->procname; ref++) {
int match = 0;
if (cur_depth && !ref->child)
continue;
if (test->procname && ref->procname &&
(strcmp(test->procname, ref->procname) == 0))
match++;
if (match) {
if (cur_depth != 0) {
cur_depth--;
ref = ref->child;
goto repeat;
}
goto out;
}
}
}
ref = NULL;
out:
sysctl_head_finish(head);
return ref;
}
static void set_fail(const char **fail, struct ctl_table *table, const char *str)
{
if (*fail) {
printk(KERN_ERR "sysctl table check failed: ");
sysctl_print_path(table);
printk(" %s\n", *fail);
dump_stack();
}
*fail = str;
}
static void sysctl_check_leaf(struct nsproxy *namespaces,
struct ctl_table *table, const char **fail)
{
struct ctl_table *ref;
ref = sysctl_check_lookup(namespaces, table);
if (ref && (ref != table))
set_fail(fail, table, "Sysctl already exists");
}
static int sysctl_check_table(struct nsproxy *namespaces, struct ctl_table *table)
static int sysctl_check_table_dups(const char *path, struct ctl_table *old,
struct ctl_table *table)
{
struct ctl_table *entry, *test;
int error = 0;
for (; table->procname; table++) {
const char *fail = NULL;
if (table->parent) {
if (!table->parent->procname)
set_fail(&fail, table, "Parent without procname");
}
if (table->child) {
if (table->data)
set_fail(&fail, table, "Directory with data?");
if (table->maxlen)
set_fail(&fail, table, "Directory with maxlen?");
if ((table->mode & (S_IRUGO|S_IXUGO)) != table->mode)
set_fail(&fail, table, "Writable sysctl directory");
if (table->proc_handler)
set_fail(&fail, table, "Directory with proc_handler");
if (table->extra1)
set_fail(&fail, table, "Directory with extra1");
if (table->extra2)
set_fail(&fail, table, "Directory with extra2");
} else {
if ((table->proc_handler == proc_dostring) ||
(table->proc_handler == proc_dointvec) ||
(table->proc_handler == proc_dointvec_minmax) ||
(table->proc_handler == proc_dointvec_jiffies) ||
(table->proc_handler == proc_dointvec_userhz_jiffies) ||
(table->proc_handler == proc_dointvec_ms_jiffies) ||
(table->proc_handler == proc_doulongvec_minmax) ||
(table->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
if (!table->data)
set_fail(&fail, table, "No data");
if (!table->maxlen)
set_fail(&fail, table, "No maxlen");
for (entry = old; entry->procname; entry++) {
for (test = table; test->procname; test++) {
if (strcmp(entry->procname, test->procname) == 0) {
printk(KERN_ERR "sysctl duplicate entry: %s/%s\n",
path, test->procname);
error = -EEXIST;
}
#ifdef CONFIG_PROC_SYSCTL
if (!table->proc_handler)
set_fail(&fail, table, "No proc_handler");
#endif
sysctl_check_leaf(namespaces, table, &fail);
}
if (table->mode > 0777)
set_fail(&fail, table, "bogus .mode");
if (fail) {
set_fail(&fail, table, NULL);
error = -EINVAL;
}
if (table->child)
error |= sysctl_check_table(namespaces, table->child);
}
return error;
}
#endif /* CONFIG_SYSCTL_SYSCALL_CHECK */
static int sysctl_check_dups(struct nsproxy *namespaces,
struct ctl_table_header *header,
const char *path, struct ctl_table *table)
{
struct ctl_table_root *root;
struct ctl_table_set *set;
struct ctl_table_header *dir_head, *head;
struct ctl_table *dir_table;
int error = 0;
/* No dups if we are the only member of our directory */
if (header->attached_by != table)
return 0;
dir_head = header->parent;
dir_table = header->attached_to;
error = sysctl_check_table_dups(path, dir_table, table);
root = &sysctl_table_root;
do {
set = lookup_header_set(root, namespaces);
list_for_each_entry(head, &set->list, ctl_entry) {
if (head->unregistering)
continue;
if (head->attached_to != dir_table)
continue;
error = sysctl_check_table_dups(path, head->attached_by,
table);
}
root = list_entry(root->root_list.next,
struct ctl_table_root, root_list);
} while (root != &sysctl_table_root);
return error;
}
static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
{
struct va_format vaf;
va_list args;
va_start(args, fmt);
vaf.fmt = fmt;
vaf.va = &args;
printk(KERN_ERR "sysctl table check failed: %s/%s %pV\n",
path, table->procname, &vaf);
va_end(args);
return -EINVAL;
}
static int sysctl_check_table(const char *path, struct ctl_table *table)
{
int err = 0;
for (; table->procname; table++) {
if (table->child)
err = sysctl_err(path, table, "Not a file");
if ((table->proc_handler == proc_dostring) ||
(table->proc_handler == proc_dointvec) ||
(table->proc_handler == proc_dointvec_minmax) ||
(table->proc_handler == proc_dointvec_jiffies) ||
(table->proc_handler == proc_dointvec_userhz_jiffies) ||
(table->proc_handler == proc_dointvec_ms_jiffies) ||
(table->proc_handler == proc_doulongvec_minmax) ||
(table->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
if (!table->data)
err = sysctl_err(path, table, "No data");
if (!table->maxlen)
err = sysctl_err(path, table, "No maxlen");
}
if (!table->proc_handler)
err = sysctl_err(path, table, "No proc_handler");
if ((table->mode & (S_IRUGO|S_IWUGO)) != table->mode)
err = sysctl_err(path, table, "bogus .mode 0%o",
table->mode);
}
return err;
}
/**
* __register_sysctl_table - register a leaf sysctl table
@ -1003,12 +949,8 @@ struct ctl_table_header *__register_sysctl_table(
header->root = root;
sysctl_set_parent(NULL, header->ctl_table);
header->count = 1;
#ifdef CONFIG_SYSCTL_SYSCALL_CHECK
if (sysctl_check_table(namespaces, header->ctl_table)) {
kfree(header);
return NULL;
}
#endif
if (sysctl_check_table(path, table))
goto fail;
spin_lock(&sysctl_lock);
header->set = lookup_header_set(root, namespaces);
header->attached_by = header->ctl_table;
@ -1029,11 +971,19 @@ struct ctl_table_header *__register_sysctl_table(
struct ctl_table_root, root_list);
set = lookup_header_set(root, namespaces);
}
if (sysctl_check_dups(namespaces, header, path, table))
goto fail_locked;
header->parent->count++;
list_add_tail(&header->ctl_entry, &header->set->list);
spin_unlock(&sysctl_lock);
return header;
fail_locked:
spin_unlock(&sysctl_lock);
fail:
kfree(header);
dump_stack();
return NULL;
}
static char *append_path(const char *path, char *pos, const char *name)

8
lib/Kconfig.debug
View File

@ -1113,14 +1113,6 @@ config LATENCYTOP
Enable this option if you want to use the LatencyTOP tool
to find out which userspace is blocking on what kernel operations.
config SYSCTL_SYSCALL_CHECK
bool "Sysctl checks"
depends on SYSCTL
---help---
sys_sysctl uses binary paths that have been found challenging
to properly maintain and use. This enables checks that help
you to keep things correct.
source mm/Kconfig.debug
source kernel/trace/Kconfig