[PATCH v2 05/14] sysctl: Add a size arg to __register_sysctl_table

Joel Granados
2023-07-31T07:21:39Z

We make these changes in order to prepare __register_sysctl_table and
its callers for when we remove the sentinel element (empty element at
the end of ctl_table arrays). We don't actually remove any sentinels in
this commit, but we *do* make sure to use ARRAY_SIZE so the table_size
is available when the removal occurs.

We add a table_size argument to __register_sysctl_table and adjust
callers, all of which pass ctl_table pointers and need an explicit call
to ARRAY_SIZE. We implement a size calculation in register_net_sysctl in
order to forward the size of the array pointer received from the network
register calls.

The new table_size argument does not yet have any effect in the
init_header call which is still dependent on the sentinel's presence.
table_size *does* however drive the `kzalloc` allocation in
__register_sysctl_table with no adverse effects as the allocated memory
is either one element greater than the calculated ctl_table array (for
the calls in ipc_sysctl.c, mq_sysctl.c and ucount.c) or the exact size
of the calculated ctl_table array (for the call from sysctl_net.c and
register_sysctl). This approach will allows us to "just" remove the
sentinel without further changes to __register_sysctl_table as
table_size will represent the exact size for all the callers at that
point.

Signed-off-by: Joel Granados <j.granados@samsung.com>
---
fs/proc/proc_sysctl.c | 23 ++++++++++++-----------
include/linux/sysctl.h | 2 +-
ipc/ipc_sysctl.c | 4 +++-
ipc/mq_sysctl.c | 4 +++-
kernel/ucount.c | 3 ++-
net/sysctl_net.c | 8 +++++++-
6 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index fa1438f1a355..b8dd78e344ff 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1312,6 +1312,7 @@ static struct ctl_dir *sysctl_mkdir_p(struct ctl_dir *dir, const char *path)
* should not be free'd after registration. So it should not be
* used on stack. It can either be a global or dynamically allocated
* by the caller and free'd later after sysctl unregistration.
+ * @table_size : The number of elements in table
*
* Register a sysctl table hierarchy. @table should be a filled in ctl_table
* array. A completely 0 filled entry terminates the table.
@@ -1354,27 +1355,20 @@ static struct ctl_dir *sysctl_mkdir_p(struct ctl_dir *dir, const char *path)
*/
struct ctl_table_header *__register_sysctl_table(
struct ctl_table_set *set,
- const char *path, struct ctl_table *table)
+ const char *path, struct ctl_table *table, size_t table_size)
{
struct ctl_table_root *root = set->dir.header.root;
struct ctl_table_header *header;
- struct ctl_table_header h_tmp;
struct ctl_dir *dir;
- struct ctl_table *entry;
struct ctl_node *node;
- int nr_entries = 0;
-
- h_tmp.ctl_table = table;
- list_for_each_table_entry(entry, (&h_tmp))
- nr_entries++;

header = kzalloc(sizeof(struct ctl_table_header) +
- sizeof(struct ctl_node)*nr_entries, GFP_KERNEL_ACCOUNT);
+ sizeof(struct ctl_node)*table_size, GFP_KERNEL_ACCOUNT);
if (!header)
return NULL;

node = (struct ctl_node *)(header + 1);
- init_header(header, root, set, node, table, nr_entries);
+ init_header(header, root, set, node, table, table_size);
if (sysctl_check_table(path, header))
goto fail;

@@ -1423,8 +1417,15 @@ struct ctl_table_header *__register_sysctl_table(
*/
struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
{
+ int count = 0;
+ struct ctl_table *entry;
+ struct ctl_table_header t_hdr;
+
+ t_hdr.ctl_table = table;
+ list_for_each_table_entry(entry, (&t_hdr))
+ count++;
return __register_sysctl_table(&sysctl_table_root.default_set,
- path, table);
+ path, table, count);
}
EXPORT_SYMBOL(register_sysctl);

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 33252ad58ebe..0495c858989f 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -226,7 +226,7 @@ extern void retire_sysctl_set(struct ctl_table_set *set);

struct ctl_table_header *__register_sysctl_table(
struct ctl_table_set *set,
- const char *path, struct ctl_table *table);
+ const char *path, struct ctl_table *table, size_t table_size);
struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table);
void unregister_sysctl_table(struct ctl_table_header * table);

diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index ef313ecfb53a..8c62e443f78b 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -259,7 +259,9 @@ bool setup_ipc_sysctls(struct ipc_namespace *ns)
tbl[i].data = NULL;
}

- ns->ipc_sysctls = __register_sysctl_table(&ns->ipc_set, "kernel", tbl);
+ ns->ipc_sysctls = __register_sysctl_table(&ns->ipc_set,
+ "kernel", tbl,
+ ARRAY_SIZE(ipc_sysctls));
}
if (!ns->ipc_sysctls) {
kfree(tbl);
diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c
index fbf6a8b93a26..ebb5ed81c151 100644
--- a/ipc/mq_sysctl.c
+++ b/ipc/mq_sysctl.c
@@ -109,7 +109,9 @@ bool setup_mq_sysctls(struct ipc_namespace *ns)
tbl[i].data = NULL;
}

- ns->mq_sysctls = __register_sysctl_table(&ns->mq_set, "fs/mqueue", tbl);
+ ns->mq_sysctls = __register_sysctl_table(&ns->mq_set,
+ "fs/mqueue", tbl,
+ ARRAY_SIZE(mq_sysctls));
}
if (!ns->mq_sysctls) {
kfree(tbl);
diff --git a/kernel/ucount.c b/kernel/ucount.c
index ee8e57fd6f90..2b80264bb79f 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -104,7 +104,8 @@ bool setup_userns_sysctls(struct user_namespace *ns)
for (i = 0; i < UCOUNT_COUNTS; i++) {
tbl[i].data = &ns->ucount_max[i];
}
- ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl);
+ ns->sysctls = __register_sysctl_table(&ns->set, "user", tbl,
+ ARRAY_SIZE(user_table));
}
if (!ns->sysctls) {
kfree(tbl);
diff --git a/net/sysctl_net.c b/net/sysctl_net.c
index 4b45ed631eb8..8ee4b74bc009 100644
--- a/net/sysctl_net.c
+++ b/net/sysctl_net.c
@@ -163,10 +163,16 @@ 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)
{
+ int count = 0;
+ struct ctl_table *entry;
+
if (!net_eq(net, &init_net))
ensure_safe_net_sysctl(net, path, table);

- return __register_sysctl_table(&net->sysctls, path, table);
+ for (entry = table; entry->procname; entry++)
+ count++;
+
+ return __register_sysctl_table(&net->sysctls, path, table, count);
}
EXPORT_SYMBOL_GPL(register_net_sysctl);

--
2.30.2