sysctl: expose proc_dointvec_minmax_sysadmin as API function

Orthogonal to the other sysctl proc functions expose the variant that is
checking CAP_SYS_ADMIN on write for consumption in external subsystem's
sysctl tables.

Signed-off-by: Levente Polyak <[email protected]>

Author: anthraxx

include/linux/sysctl.h

@@ -53,6 +53,8 @@ int proc_douintvec(struct ctl_table *, int, void *, size_t *, loff_t *);
 int proc_dointvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);
 int proc_douintvec_minmax(struct ctl_table *table, int write, void *buffer,
 		size_t *lenp, loff_t *ppos);
+int proc_dointvec_minmax_sysadmin(struct ctl_table *table, int write,
+				  void *buffer, size_t *lenp, loff_t *ppos);
 int proc_dointvec_jiffies(struct ctl_table *, int, void *, size_t *, loff_t *);
 int proc_dointvec_userhz_jiffies(struct ctl_table *, int, void *, size_t *,
 		loff_t *);

kernel/sysctl.c

@@ -896,16 +896,34 @@ static int proc_taint(struct ctl_table *table, int write,
 	return err;
 }
 
-#ifdef CONFIG_PRINTK
-static int proc_dointvec_minmax_sysadmin(struct ctl_table *table, int write,
+/**
+ * proc_dointvec_minmax_sysadmin - read a vector of integers with min/max values
+ * checking CAP_SYS_ADMIN on write
+ * @table: the sysctl table
+ * @write: %TRUE if this is a write to the sysctl file
+ * @buffer: the user buffer
+ * @lenp: the size of the user buffer
+ * @ppos: file position
+ *
+ * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
+ * values from/to the user buffer, treated as an ASCII string.
+ *
+ * This routine will ensure the values are within the range specified by
+ * table->extra1 (min) and table->extra2 (max).
+ *
+ * Writing is only allowed when root has CAP_SYS_ADMIN.
+ *
+ * Returns 0 on success, -EPERM on permission failure or -EINVAL on write
+ * when the range check fails.
+ */
+int proc_dointvec_minmax_sysadmin(struct ctl_table *table, int write,
 				void *buffer, size_t *lenp, loff_t *ppos)
 {
 	if (write && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
 	return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 }
-#endif
 
 /**
  * struct do_proc_dointvec_minmax_conv_param - proc_dointvec_minmax() range checking structure
@@ -1591,6 +1609,12 @@ int proc_douintvec_minmax(struct ctl_table *table, int write,
 	return -ENOSYS;
 }
 
+int proc_dointvec_minmax_sysadmin(struct ctl_table *table, int write,
+				  void *buffer, size_t *lenp, loff_t *ppos)
+{
+	return -ENOSYS;
+}
+
 int proc_dointvec_jiffies(struct ctl_table *table, int write,
 		    void *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -3464,6 +3488,7 @@ EXPORT_SYMBOL(proc_douintvec);
 EXPORT_SYMBOL(proc_dointvec_jiffies);
 EXPORT_SYMBOL(proc_dointvec_minmax);
 EXPORT_SYMBOL_GPL(proc_douintvec_minmax);
+EXPORT_SYMBOL(proc_dointvec_minmax_sysadmin);
 EXPORT_SYMBOL(proc_dointvec_userhz_jiffies);
 EXPORT_SYMBOL(proc_dointvec_ms_jiffies);
 EXPORT_SYMBOL(proc_dostring);