[PATCH v2 08/14] sysctl: Add size to register_net_sysctl function

Joel Granados
2023-07-31T07:20:33Z

This commit adds size to the register_net_sysctl indirection function to
facilitate the removal of the sentinel elements (last empty markers)
from the ctl_table arrays. Though we don't actually remove any sentinels
in this commit, register_net_sysctl* now has the capability of
forwarding table_size for when that happens.

We create a new function register_net_sysctl_sz with an extra size
argument. A macro replaces the existing register_net_sysctl. The size in
the macro is SIZE_MAX instead of ARRAY_SIZE to avoid compilation errors
while we systematically migrate to register_net_sysctl_sz. Will change
to ARRAY_SIZE in subsequent commits.

Care is taken to add table_size to the stopping criteria in such a way
that when we remove the empty sentinel element, it will continue
stopping in the last element of the ctl_table array.

Signed-off-by: Joel Granados <j.granados@samsung.com>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/net_namespace.h | 10 ++++++----
net/sysctl_net.c | 22 +++++++++++++---------
2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 78beaa765c73..e4e5fe75a281 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -469,15 +469,17 @@ void unregister_pernet_device(struct pernet_operations *);

struct ctl_table;

+#define register_net_sysctl(net, path, table) \
+ register_net_sysctl_sz(net, path, table, SIZE_MAX)
#ifdef CONFIG_SYSCTL
int net_sysctl_init(void);
-struct ctl_table_header *register_net_sysctl(struct net *net, const char *path,
- struct ctl_table *table);
+struct ctl_table_header *register_net_sysctl_sz(struct net *net, const char *path,
+ struct ctl_table *table, size_t table_size);
void unregister_net_sysctl_table(struct ctl_table_header *header);
#else
static inline int net_sysctl_init(void) { return 0; }
-static inline struct ctl_table_header *register_net_sysctl(struct net *net,
- const char *path, struct ctl_table *table)
+static inline struct ctl_table_header *register_net_sysctl_sz(struct net *net,
+ const char *path, struct ctl_table *table, size_t table_size)
{
return NULL;
}
diff --git a/net/sysctl_net.c b/net/sysctl_net.c
index d9cbbb51b143..051ed5f6fc93 100644
--- a/net/sysctl_net.c
+++ b/net/sysctl_net.c
@@ -122,12 +122,13 @@ __init int net_sysctl_init(void)
* allocated.
*/
static void ensure_safe_net_sysctl(struct net *net, const char *path,
- struct ctl_table *table)
+ struct ctl_table *table, size_t table_size)
{
struct ctl_table *ent;

pr_debug("Registering net sysctl (net %p): %s\n", net, path);
- for (ent = table; ent->procname; ent++) {
+ ent = table;
+ for (size_t i = 0; i < table_size && ent->procname; ent++, i++) {
unsigned long addr;
const char *where;

@@ -160,21 +161,24 @@ static void ensure_safe_net_sysctl(struct net *net, const char *path,
}
}

-struct ctl_table_header *register_net_sysctl(struct net *net,
- const char *path, struct ctl_table *table)
+struct ctl_table_header *register_net_sysctl_sz(struct net *net,
+ const char *path,
+ struct ctl_table *table,
+ size_t table_size)
{
- int count = 0;
+ int count;
struct ctl_table *entry;

if (!net_eq(net, &init_net))
- ensure_safe_net_sysctl(net, path, table);
+ ensure_safe_net_sysctl(net, path, table, table_size);

- for (entry = table; entry->procname; entry++)
- count++;
+ entry = table;
+ for (count = 0 ; count < table_size && entry->procname; entry++, count++)
+ ;

return __register_sysctl_table(&net->sysctls, path, table, count);
}
-EXPORT_SYMBOL_GPL(register_net_sysctl);
+EXPORT_SYMBOL_GPL(register_net_sysctl_sz);

void unregister_net_sysctl_table(struct ctl_table_header *header)
{
--
2.30.2