linux-kernel - [RFC PATCH 2/4] sysctl: add helper functions to extract table->extra1/extra2

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Message-Id: <9ebbce66874c884f7112476bfd4132510d06854c.1768324215.git.wen.yang@linux.dev>
Date: Wed, 14 Jan 2026 01:40:31 +0800
From: wen.yang@...ux.dev
To: Joel Granados <joel.granados@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	Wen Yang <wen.yang@...ux.dev>
Subject: [RFC PATCH 2/4] sysctl: add helper functions to extract table->extra1/extra2

From: Wen Yang <wen.yang@...ux.dev>

Add some sysctl helper functions to avoid direct access to
table->extra1/extra2.

No functional change intended.

Selftest were also made:
[14:52:13] ================ sysctl_test (10 subtests) =================
[14:52:13] [PASSED] sysctl_test_api_dointvec_null_tbl_data
[14:52:13] [PASSED] sysctl_test_api_dointvec_table_maxlen_unset
[14:52:13] [PASSED] sysctl_test_api_dointvec_table_len_is_zero
[14:52:13] [PASSED] sysctl_test_api_dointvec_table_read_but_position_set
[14:52:13] [PASSED] sysctl_test_dointvec_read_happy_single_positive
[14:52:13] [PASSED] sysctl_test_dointvec_read_happy_single_negative
[14:52:13] [PASSED] sysctl_test_dointvec_write_happy_single_positive
[14:52:13] [PASSED] sysctl_test_dointvec_write_happy_single_negative
[14:52:13] [PASSED] sysctl_test_api_dointvec_write_single_less_int_min
[14:52:13] [PASSED] sysctl_test_api_dointvec_write_single_greater_int_max
[14:52:13] =================== [PASSED] sysctl_test ===================
[14:52:13] ============================================================
[14:52:13] Testing complete. Ran 10 tests: passed: 10

Suggested-by: Joel Granados <joel.granados@...nel.org>
Signed-off-by: Wen Yang <wen.yang@...ux.dev>
---
 include/linux/sysctl.h | 10 ++++++++++
 kernel/sysctl.c        | 14 ++++----------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 683422bc3e7f..9690740885ab 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -164,6 +164,16 @@ static inline void *proc_sys_poll_event(struct ctl_table_poll *poll)
 #define DEFINE_CTL_TABLE_POLL(name)					\
 	struct ctl_table_poll name = __CTL_TABLE_POLL_INITIALIZER(name)
 
+#define SYSCTL_IN_RANGE(tbl, val, type) \
+	((tbl) && \
+	 (!(tbl)->extra1 || (*(type *)(tbl)->extra1 <= (type)(val))) && \
+	 (!(tbl)->extra2 || (*(type *)(tbl)->extra2 >= (type)(val))))
+
+#define SYSCTL_IN_RANGE_INT(tbl, val)           SYSCTL_IN_RANGE(tbl, val, int)
+#define SYSCTL_IN_RANGE_LONG(tbl, val)          SYSCTL_IN_RANGE(tbl, val, long)
+#define SYSCTL_IN_RANGE_UINT(tbl, val)          SYSCTL_IN_RANGE(tbl, val, unsigned int)
+#define SYSCTL_IN_RANGE_ULONG(tbl, val)         SYSCTL_IN_RANGE(tbl, val, unsigned long)
+
 /* A sysctl table is an array of struct ctl_table: */
 struct ctl_table {
 	const char *procname;		/* Text ID for /proc/sys */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 2e769550b268..990e692f626b 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -428,10 +428,7 @@ int proc_uint_conv(ulong *u_ptr, uint *k_ptr, int dir,
 		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))
+		if (!SYSCTL_IN_RANGE_UINT(tbl, tmp_k))
 			return -ERANGE;
 		WRITE_ONCE(*k_ptr, tmp_k);
 	} else
@@ -531,8 +528,7 @@ int proc_int_conv(bool *negp, ulong *u_ptr, int *k_ptr, int dir,
 		ret = user_to_kern(negp, u_ptr, &tmp_k);
 		if (ret)
 			return ret;
-		if ((tbl->extra1 && *(int *)tbl->extra1 > tmp_k) ||
-		    (tbl->extra2 && *(int *)tbl->extra2 < tmp_k))
+		if (!SYSCTL_IN_RANGE_INT(tbl, tmp_k))
 			return -EINVAL;
 		WRITE_ONCE(*k_ptr, tmp_k);
 	} else
@@ -969,7 +965,7 @@ static int do_proc_doulongvec_minmax(const struct ctl_table *table, int dir,
 				     unsigned long convmul,
 				     unsigned long convdiv)
 {
-	unsigned long *i, *min, *max;
+	unsigned long *i ;
 	int vleft, first = 1, err = 0;
 	size_t left;
 	char *p;
@@ -981,8 +977,6 @@ static int do_proc_doulongvec_minmax(const struct ctl_table *table, int dir,
 	}
 
 	i = table->data;
-	min = table->extra1;
-	max = table->extra2;
 	vleft = table->maxlen / sizeof(unsigned long);
 	left = *lenp;
 
@@ -1014,7 +1008,7 @@ static int do_proc_doulongvec_minmax(const struct ctl_table *table, int dir,
 			}
 
 			val = convmul * val / convdiv;
-			if ((min && val < *min) || (max && val > *max)) {
+			if (!SYSCTL_IN_RANGE_ULONG(table, val)) {
 				err = -EINVAL;
 				break;
 			}
-- 
2.25.1