sysctl: Replace UINT converter macros with functions

Replace the SYSCTL_USER_TO_KERN_UINT_CONV and SYSCTL_UINT_CONV_CUSTOM
macros with functions with the same logic. This makes debugging easier
and aligns with the functions preference described in coding-style.rst.
Update the only user of this API: pipe.c.

Signed-off-by: Joel Granados <joel.granados@kernel.org>

1 files changed, 123 insertions, 17 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 4ea56c71c7ef..00df21b84900 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -354,29 +354,117 @@ static void proc_put_char(void **buf, size_t *size, char c)
 	}
 }
 
-static SYSCTL_USER_TO_KERN_INT_CONV(, SYSCTL_CONV_IDENTITY)
-static SYSCTL_KERN_TO_USER_INT_CONV(, SYSCTL_CONV_IDENTITY)
-
-static SYSCTL_INT_CONV_CUSTOM(, sysctl_user_to_kern_int_conv,
-			      sysctl_kern_to_user_int_conv, false)
-static SYSCTL_INT_CONV_CUSTOM(_minmax, sysctl_user_to_kern_int_conv,
-			      sysctl_kern_to_user_int_conv, true)
+/**
+ * proc_uint_u2k_conv_uop - Assign user value to a kernel pointer
+ *
+ * @u_ptr: pointer to user space variable
+ * @k_ptr: pointer to kernel variable
+ * @u_ptr_op: execute this function before assigning to k_ptr
+ *
+ * Uses WRITE_ONCE to assign value to k_ptr. Executes u_ptr_op if
+ * not NULL. Check that the values are less than UINT_MAX to avoid
+ * having to support wrap around from userspace.
+ *
+ * returns 0 on success.
+ */
+int proc_uint_u2k_conv_uop(const ulong *u_ptr, uint *k_ptr,
+			   ulong (*u_ptr_op)(const ulong))
+{
+	ulong u = u_ptr_op ? u_ptr_op(*u_ptr) : *u_ptr;
 
+	if (u > UINT_MAX)
+		return -EINVAL;
+	WRITE_ONCE(*k_ptr, u);
+	return 0;
+}
 
-static SYSCTL_USER_TO_KERN_UINT_CONV(, SYSCTL_CONV_IDENTITY)
+/**
+ * proc_uint_k2u_conv - Assign kernel value to a user space pointer
+ *
+ * @u_ptr: pointer to user space variable
+ * @k_ptr: pointer to kernel variable
+ *
+ * Uses READ_ONCE to assign value to u_ptr.
+ *
+ * returns 0 on success.
+ */
+int proc_uint_k2u_conv(ulong *u_ptr, const uint *k_ptr)
+{
+	uint val = READ_ONCE(*k_ptr);
+	*u_ptr = (ulong)val;
+	return 0;
+}
 
-int sysctl_kern_to_user_uint_conv(unsigned long *u_ptr,
-				  const unsigned int *k_ptr)
+/**
+ * proc_uint_conv - Change user or kernel pointer based on direction
+ *
+ * @u_ptr: pointer to user variable
+ * @k_ptr: pointer to kernel variable
+ * @dir: %TRUE if this is a write to the sysctl file
+ * @tbl: the sysctl table
+ * @k_ptr_range_check: Check range for k_ptr when %TRUE
+ * @user_to_kern: Callback used to assign value from user to kernel var
+ * @kern_to_user: Callback used to assign value from kernel to user var
+ *
+ * When direction is kernel to user, then the u_ptr is modified.
+ * When direction is user to kernel, then the k_ptr is modified.
+ *
+ * Returns 0 on success
+ */
+int proc_uint_conv(ulong *u_ptr, uint *k_ptr, int dir,
+		   const struct ctl_table *tbl, bool k_ptr_range_check,
+		   int (*user_to_kern)(const ulong *u_ptr, uint *k_ptr),
+		   int (*kern_to_user)(ulong *u_ptr, const uint *k_ptr))
 {
-	unsigned int val = READ_ONCE(*k_ptr);
-	*u_ptr = (unsigned long)val;
+	if (SYSCTL_KERN_TO_USER(dir))
+		return kern_to_user(u_ptr, k_ptr);
+
+	if (k_ptr_range_check) {
+		uint tmp_k;
+		int ret;
+
+		if (!tbl)
+			return -EINVAL;
+		ret = user_to_kern(u_ptr, &tmp_k);
+		if (ret)
+			return ret;
+		if ((tbl->extra1 &&
+		     *(uint *)tbl->extra1 > tmp_k) ||
+		    (tbl->extra2 &&
+		     *(uint *)tbl->extra2 < tmp_k))
+			return -ERANGE;
+		WRITE_ONCE(*k_ptr, tmp_k);
+	} else
+		return user_to_kern(u_ptr, k_ptr);
 	return 0;
 }
 
-static SYSCTL_UINT_CONV_CUSTOM(, sysctl_user_to_kern_uint_conv,
-			       sysctl_kern_to_user_uint_conv, false)
-static SYSCTL_UINT_CONV_CUSTOM(_minmax, sysctl_user_to_kern_uint_conv,
-			       sysctl_kern_to_user_uint_conv, true)
+static int proc_uint_u2k_conv(const ulong *u_ptr, uint *k_ptr)
+{
+	return proc_uint_u2k_conv_uop(u_ptr, k_ptr, NULL);
+}
+
+static int do_proc_uint_conv(ulong *u_ptr, uint *k_ptr, int dir,
+			     const struct ctl_table *tbl)
+{
+	return proc_uint_conv(u_ptr, k_ptr, dir, tbl, false,
+			      proc_uint_u2k_conv, proc_uint_k2u_conv);
+}
+
+static int do_proc_uint_conv_minmax(ulong *u_ptr, uint *k_ptr, int dir,
+				    const struct ctl_table *tbl)
+{
+	return proc_uint_conv(u_ptr, k_ptr, dir, tbl, true,
+			      proc_uint_u2k_conv, proc_uint_k2u_conv);
+}
+
+static SYSCTL_USER_TO_KERN_INT_CONV(, SYSCTL_CONV_IDENTITY)
+static SYSCTL_KERN_TO_USER_INT_CONV(, SYSCTL_CONV_IDENTITY)
+
+static SYSCTL_INT_CONV_CUSTOM(, sysctl_user_to_kern_int_conv,
+			      sysctl_kern_to_user_int_conv, false)
+static SYSCTL_INT_CONV_CUSTOM(_minmax, sysctl_user_to_kern_int_conv,
+			      sysctl_kern_to_user_int_conv, true)
 
 static const char proc_wspace_sep[] = { ' ', '\t', '\n' };
 
@@ -576,7 +664,6 @@ int proc_douintvec_conv(const struct ctl_table *table, int dir, void *buffer,
 	return do_proc_douintvec(table, dir, buffer, lenp, ppos, conv);
 }
 
-
 /**
  * proc_dobool - read/write a bool
  * @table: the sysctl table
@@ -1079,6 +1166,25 @@ int proc_douintvec_conv(const struct ctl_table *table, int write, void *buffer,
 	return -ENOSYS;
 }
 
+int proc_uint_k2u_conv(ulong *u_ptr, const uint *k_ptr)
+{
+	return -ENOSYS;
+}
+
+int proc_uint_u2k_conv_uop(const ulong *u_ptr, uint *k_ptr,
+			   ulong (*u_ptr_op)(const ulong))
+{
+	return -ENOSYS;
+}
+
+int proc_uint_conv(ulong *u_ptr, uint *k_ptr, int dir,
+		   const struct ctl_table *tbl, bool k_ptr_range_check,
+		   int (*user_to_kern)(const ulong *u_ptr, uint *k_ptr),
+		   int (*kern_to_user)(ulong *u_ptr, const uint *k_ptr))
+{
+	return -ENOSYS;
+}
+
 int proc_dou8vec_minmax(const struct ctl_table *table, int dir,
 			void *buffer, size_t *lenp, loff_t *ppos)
 {