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Subject[PATCH 1/1] kernel/ucounts: expose current inotify watch count
Date
Adds a readonly 'current_inotify_watches' entry to the user sysctl table.
The handler for this entry is a custom function that ends calling
proc_dointvec.

Signed-off-by: Albert Vaca Cintora <albertvaka@gmail.com>
---
kernel/ucount.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)

diff --git a/kernel/ucount.c b/kernel/ucount.c
index f48d1b6376a4..afa3b89e3373 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -57,6 +57,11 @@ static struct ctl_table_root set_root = {
.permissions = set_permissions,
};

+#ifdef CONFIG_INOTIFY_USER
+int proc_read_inotify_watches(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
+#endif
+
static int zero = 0;
static int int_max = INT_MAX;
#define UCOUNT_ENTRY(name) \
@@ -79,6 +84,12 @@ static struct ctl_table user_table[] = {
#ifdef CONFIG_INOTIFY_USER
UCOUNT_ENTRY("max_inotify_instances"),
UCOUNT_ENTRY("max_inotify_watches"),
+ {
+ .procname = "current_inotify_watches",
+ .maxlen = sizeof(int),
+ .mode = 0444,
+ .proc_handler = proc_read_inotify_watches,
+ },
#endif
{ }
};
@@ -226,6 +237,24 @@ void dec_ucount(struct ucounts *ucounts, enum ucount_type type)
put_ucounts(ucounts);
}

+#ifdef CONFIG_INOTIFY_USER
+int proc_read_inotify_watches(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct ucounts *ucounts;
+ struct ctl_table fake_table;
+ int count;
+
+ ucounts = get_ucounts(current_user_ns(), current_euid());
+ count = atomic_read(&ucounts->ucount[UCOUNT_INOTIFY_WATCHES]);
+ put_ucounts(ucounts);
+
+ fake_table.data = &count;
+ fake_table.maxlen = sizeof(count);
+ return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
+}
+#endif
+
static __init int user_namespace_sysctl_init(void)
{
#ifdef CONFIG_SYSCTL
--
2.20.1
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