[PATCH v5] sysctl: simplify the min/max boundary check

[Wen Yang <wen.yang@linux.dev>]

do_proc_dointvec_conv() used the default range of int type, while
do_proc_dointvec_minmax_conv() additionally used "int * {min, max}" of
struct do_proc_dointvec_minmax_conv_param, which are actually passed
in table->extra{1,2} pointers.

By changing the struct do_proc_dointvec_minmax_conv_param's
"int * {min, max}" to "int {min, max}" and setting the min/max value
via dereference the table->extra{1, 2}, those do_proc_dointvec_conv() and
do_proc_dointvec_minmax_conv() functions can be merged into one and reduce
code by one-third.

Similar changes were also made for do_proc_douintvec_minmax_conv_param,
do_proc_douintvec_conv() and do_proc_douintvec_minmax_conv().

Selftest were also made:

[23:16:38] ================ sysctl_test (11 subtests) =================
[23:16:38] [PASSED] sysctl_test_api_dointvec_null_tbl_data
[23:16:38] [PASSED] sysctl_test_api_dointvec_table_maxlen_unset
[23:16:38] [PASSED] sysctl_test_api_dointvec_table_len_is_zero
[23:16:38] [PASSED] sysctl_test_api_dointvec_table_read_but_position_set
[23:16:38] [PASSED] sysctl_test_dointvec_read_happy_single_positive
[23:16:38] [PASSED] sysctl_test_dointvec_read_happy_single_negative
[23:16:38] [PASSED] sysctl_test_dointvec_write_happy_single_positive
[23:16:38] [PASSED] sysctl_test_dointvec_write_happy_single_negative
[23:16:38] [PASSED] sysctl_test_api_dointvec_write_single_less_int_min
[23:16:38] [PASSED] sysctl_test_api_dointvec_write_single_greater_int_max
[23:16:38] [PASSED] sysctl_test_register_sysctl_sz_invalid_extra_value
[23:16:38] =================== [PASSED] sysctl_test ===================
[23:16:38] ============================================================
[23:16:38] Testing complete. Ran 11 tests: passed: 11

Signed-off-by: Wen Yang <wen.yang@linux.dev>
Cc: Joel Granados <joel.granados@kernel.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: linux-kernel@vger.kernel.org
---
 kernel/sysctl.c | 211 ++++++++++++++++++++----------------------------
 1 file changed, 86 insertions(+), 125 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 7ae7a4136855..250dc9057259 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -424,22 +424,44 @@ static void proc_put_char(void **buf, size_t *size, char c)
 	}
 }
 
-static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
-				 int *valp,
-				 int write, void *data)
+/**
+ * struct do_proc_dointvec_minmax_conv_param - proc_dointvec_minmax() range checking structure
+ * @min: the minimum allowable value
+ * @max: the maximum allowable value
+ *
+ * The do_proc_dointvec_minmax_conv_param structure provides the
+ * minimum and maximum values for doing range checking for those sysctl
+ * parameters that use the proc_dointvec_minmax(), proc_dou8vec_minmax() and so on.
+ */
+struct do_proc_dointvec_minmax_conv_param {
+	int min;
+	int max;
+};
+
+static inline int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp,
+		int *valp,
+		int write, void *data)
 {
+	struct do_proc_dointvec_minmax_conv_param *param = data;
+	long min, max;
+	long val;
+
 	if (write) {
 		if (*negp) {
-			if (*lvalp > (unsigned long) INT_MAX + 1)
-				return -EINVAL;
-			WRITE_ONCE(*valp, -*lvalp);
+			max = param ? param->max : 0;
+			min = param ? param->min : INT_MIN;
+			val = -*lvalp;
 		} else {
-			if (*lvalp > (unsigned long) INT_MAX)
-				return -EINVAL;
-			WRITE_ONCE(*valp, *lvalp);
+			max = param ? param->max : INT_MAX;
+			min = param ? param->min : 0;
+			val = *lvalp;
 		}
+
+		if (val > max || val < min)
+			return -EINVAL;
+		WRITE_ONCE(*valp, (int)val);
 	} else {
-		int val = READ_ONCE(*valp);
+		val = (int)READ_ONCE(*valp);
 		if (val < 0) {
 			*negp = true;
 			*lvalp = -(unsigned long)val;
@@ -448,21 +470,44 @@ static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
 			*lvalp = (unsigned long)val;
 		}
 	}
+
 	return 0;
 }
 
-static int do_proc_douintvec_conv(unsigned long *lvalp,
-				  unsigned int *valp,
-				  int write, void *data)
+/**
+ * struct do_proc_douintvec_minmax_conv_param - proc_douintvec_minmax() range checking structure
+ * @min: minimum allowable value
+ * @max: maximum allowable value
+ *
+ * The do_proc_douintvec_minmax_conv_param structure provides the
+ * minimum and maximum values for doing range checking for those sysctl
+ * parameters that use the proc_douintvec_minmax() handler.
+ */
+struct do_proc_douintvec_minmax_conv_param {
+	unsigned int min;
+	unsigned int max;
+};
+
+static inline int do_proc_douintvec_minmax_conv(unsigned long *lvalp,
+					 unsigned int *valp,
+					 int write, void *data)
 {
+	struct do_proc_douintvec_minmax_conv_param *param = data;
+	unsigned long min, max;
+
 	if (write) {
-		if (*lvalp > UINT_MAX)
+		max = param ? param->max : UINT_MAX;
+		min = param ? param->min : 0;
+
+		if (*lvalp > max || *lvalp < min)
 			return -EINVAL;
-		WRITE_ONCE(*valp, *lvalp);
+
+		WRITE_ONCE(*valp, (unsigned int)*lvalp);
 	} else {
 		unsigned int val = READ_ONCE(*valp);
 		*lvalp = (unsigned long)val;
 	}
+
 	return 0;
 }
 
@@ -489,7 +534,7 @@ static int __do_proc_dointvec(void *tbl_data, const struct ctl_table *table,
 	left = *lenp;
 
 	if (!conv)
-		conv = do_proc_dointvec_conv;
+		conv = do_proc_dointvec_minmax_conv;
 
 	if (write) {
 		if (proc_first_pos_non_zero_ignore(ppos, table))
@@ -667,7 +712,7 @@ static int __do_proc_douintvec(void *tbl_data, const struct ctl_table *table,
 	}
 
 	if (!conv)
-		conv = do_proc_douintvec_conv;
+		conv = do_proc_douintvec_minmax_conv;
 
 	if (write)
 		return do_proc_douintvec_w(i, table, buffer, lenp, ppos,
@@ -762,7 +807,7 @@ int proc_douintvec(const struct ctl_table *table, int write, void *buffer,
 		size_t *lenp, loff_t *ppos)
 {
 	return do_proc_douintvec(table, write, buffer, lenp, ppos,
-				 do_proc_douintvec_conv, NULL);
+				 do_proc_douintvec_minmax_conv, NULL);
 }
 
 /*
@@ -808,46 +853,6 @@ static int proc_taint(const struct ctl_table *table, int write,
 	return err;
 }
 
-/**
- * struct do_proc_dointvec_minmax_conv_param - proc_dointvec_minmax() range checking structure
- * @min: pointer to minimum allowable value
- * @max: pointer to maximum allowable value
- *
- * The do_proc_dointvec_minmax_conv_param structure provides the
- * minimum and maximum values for doing range checking for those sysctl
- * parameters that use the proc_dointvec_minmax() handler.
- */
-struct do_proc_dointvec_minmax_conv_param {
-	int *min;
-	int *max;
-};
-
-static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp,
-					int *valp,
-					int write, void *data)
-{
-	int tmp, ret;
-	struct do_proc_dointvec_minmax_conv_param *param = data;
-	/*
-	 * If writing, first do so via a temporary local int so we can
-	 * bounds-check it before touching *valp.
-	 */
-	int *ip = write ? &tmp : valp;
-
-	ret = do_proc_dointvec_conv(negp, lvalp, ip, write, data);
-	if (ret)
-		return ret;
-
-	if (write) {
-		if ((param->min && *param->min > tmp) ||
-		    (param->max && *param->max < tmp))
-			return -EINVAL;
-		WRITE_ONCE(*valp, tmp);
-	}
-
-	return 0;
-}
-
 /**
  * proc_dointvec_minmax - read a vector of integers with min/max values
  * @table: the sysctl table
@@ -867,53 +872,14 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp,
 int proc_dointvec_minmax(const struct ctl_table *table, int write,
 		  void *buffer, size_t *lenp, loff_t *ppos)
 {
-	struct do_proc_dointvec_minmax_conv_param param = {
-		.min = (int *) table->extra1,
-		.max = (int *) table->extra2,
-	};
+	struct do_proc_dointvec_minmax_conv_param param;
+
+	param.min = (table->extra1) ? *(int *) table->extra1 : INT_MIN;
+	param.max = (table->extra2) ? *(int *) table->extra2 : INT_MAX;
 	return do_proc_dointvec(table, write, buffer, lenp, ppos,
 				do_proc_dointvec_minmax_conv, &param);
 }
 
-/**
- * struct do_proc_douintvec_minmax_conv_param - proc_douintvec_minmax() range checking structure
- * @min: pointer to minimum allowable value
- * @max: pointer to maximum allowable value
- *
- * The do_proc_douintvec_minmax_conv_param structure provides the
- * minimum and maximum values for doing range checking for those sysctl
- * parameters that use the proc_douintvec_minmax() handler.
- */
-struct do_proc_douintvec_minmax_conv_param {
-	unsigned int *min;
-	unsigned int *max;
-};
-
-static int do_proc_douintvec_minmax_conv(unsigned long *lvalp,
-					 unsigned int *valp,
-					 int write, void *data)
-{
-	int ret;
-	unsigned int tmp;
-	struct do_proc_douintvec_minmax_conv_param *param = data;
-	/* write via temporary local uint for bounds-checking */
-	unsigned int *up = write ? &tmp : valp;
-
-	ret = do_proc_douintvec_conv(lvalp, up, write, data);
-	if (ret)
-		return ret;
-
-	if (write) {
-		if ((param->min && *param->min > tmp) ||
-		    (param->max && *param->max < tmp))
-			return -ERANGE;
-
-		WRITE_ONCE(*valp, tmp);
-	}
-
-	return 0;
-}
-
 /**
  * proc_douintvec_minmax - read a vector of unsigned ints with min/max values
  * @table: the sysctl table
@@ -936,10 +902,11 @@ static int do_proc_douintvec_minmax_conv(unsigned long *lvalp,
 int proc_douintvec_minmax(const struct ctl_table *table, int write,
 			  void *buffer, size_t *lenp, loff_t *ppos)
 {
-	struct do_proc_douintvec_minmax_conv_param param = {
-		.min = (unsigned int *) table->extra1,
-		.max = (unsigned int *) table->extra2,
-	};
+	struct do_proc_douintvec_minmax_conv_param param;
+
+	param.min = (table->extra1) ? *(unsigned int *) table->extra1 : 0;
+	param.max = (table->extra2) ? *(unsigned int *) table->extra2 : UINT_MAX;
+
 	return do_proc_douintvec(table, write, buffer, lenp, ppos,
 				 do_proc_douintvec_minmax_conv, &param);
 }
@@ -965,23 +932,17 @@ int proc_dou8vec_minmax(const struct ctl_table *table, int write,
 			void *buffer, size_t *lenp, loff_t *ppos)
 {
 	struct ctl_table tmp;
-	unsigned int min = 0, max = 255U, val;
+	unsigned int val;
 	u8 *data = table->data;
-	struct do_proc_douintvec_minmax_conv_param param = {
-		.min = &min,
-		.max = &max,
-	};
+	struct do_proc_douintvec_minmax_conv_param param;
 	int res;
 
 	/* Do not support arrays yet. */
 	if (table->maxlen != sizeof(u8))
 		return -EINVAL;
 
-	if (table->extra1)
-		min = *(unsigned int *) table->extra1;
-	if (table->extra2)
-		max = *(unsigned int *) table->extra2;
-
+	param.min = (table->extra1) ? *(unsigned int *) table->extra1 : 0;
+	param.max = (table->extra2) ? *(unsigned int *) table->extra2 : 255U;
 	tmp = *table;
 
 	tmp.maxlen = sizeof(val);
@@ -1022,7 +983,7 @@ static int __do_proc_doulongvec_minmax(void *data,
 		void *buffer, size_t *lenp, loff_t *ppos,
 		unsigned long convmul, unsigned long convdiv)
 {
-	unsigned long *i, *min, *max;
+	unsigned long *i, min, max;
 	int vleft, first = 1, err = 0;
 	size_t left;
 	char *p;
@@ -1033,8 +994,9 @@ static int __do_proc_doulongvec_minmax(void *data,
 	}
 
 	i = data;
-	min = table->extra1;
-	max = table->extra2;
+	min = (table->extra1) ? *(unsigned long *) table->extra1 : 0;
+	max = (table->extra2) ? *(unsigned long *) table->extra2 : ULONG_MAX;
+
 	vleft = table->maxlen / sizeof(unsigned long);
 	left = *lenp;
 
@@ -1066,7 +1028,7 @@ static int __do_proc_doulongvec_minmax(void *data,
 			}
 
 			val = convmul * val / convdiv;
-			if ((min && val < *min) || (max && val > *max)) {
+			if ((val < min) || (val > max)) {
 				err = -EINVAL;
 				break;
 			}
@@ -1236,8 +1198,7 @@ static int do_proc_dointvec_ms_jiffies_minmax_conv(bool *negp, unsigned long *lv
 		return ret;
 
 	if (write) {
-		if ((param->min && *param->min > tmp) ||
-				(param->max && *param->max < tmp))
+		if ((param->min > tmp) || (param->max < tmp))
 			return -EINVAL;
 		*valp = tmp;
 	}
@@ -1269,10 +1230,10 @@ int proc_dointvec_jiffies(const struct ctl_table *table, int write,
 int proc_dointvec_ms_jiffies_minmax(const struct ctl_table *table, int write,
 			  void *buffer, size_t *lenp, loff_t *ppos)
 {
-	struct do_proc_dointvec_minmax_conv_param param = {
-		.min = (int *) table->extra1,
-		.max = (int *) table->extra2,
-	};
+	struct do_proc_dointvec_minmax_conv_param param;
+
+	param.min = (table->extra1) ? *(int *) table->extra1 : INT_MIN;
+	param.max = (table->extra2) ? *(int *) table->extra2 : INT_MAX;
 	return do_proc_dointvec(table, write, buffer, lenp, ppos,
 			do_proc_dointvec_ms_jiffies_minmax_conv, &param);
 }
-- 
2.25.1