From: "Luis R. Rodriguez" <mcgrof@kernel.org>

Date: Wed, 12 Jul 2017 14:33:33 -0700

Subject: [PATCH 05/14] sysctl: fold sysctl_writes_strict checks into helper

Git-commit: d383d48470819e86fe30eb72f0e9494e1ee0e2af

Patch-mainline: v4.13-rc1

References: bsc#1048893

The mode sysctl_writes_strict positional checks keep being copy and pasted

as we add new proc handlers.  Just add a helper to avoid code duplication.

Link: http://lkml.kernel.org/r/20170519033554.18592-4-mcgrof@kernel.org

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>

Suggested-by: Kees Cook <keescook@chromium.org>

Cc: Al Viro <viro@zeniv.linux.org.uk>

Cc: "Eric W. Biederman" <ebiederm@xmission.com>

Cc: Alexey Dobriyan <adobriyan@gmail.com>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>

---

 kernel/sysctl.c | 56 ++++++++++++++++++++++++++++++++------------------------

 1 file changed, 32 insertions(+), 24 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c

index 00c582a05dc0..b47a479de51d 100644

--- a/kernel/sysctl.c

+++ b/kernel/sysctl.c

@@ -1973,6 +1973,32 @@ static void warn_sysctl_write(struct ctl_table *table)

 }

 /**

+ * proc_first_pos_non_zero_ignore - check if firs position is allowed

+ * @ppos: file position

+ * @table: the sysctl table

+ *

+ * Returns true if the first position is non-zero and the sysctl_writes_strict

+ * mode indicates this is not allowed for numeric input types. String proc

+ * hadlers can ignore the return value.

+ */

+static bool proc_first_pos_non_zero_ignore(loff_t *ppos,

+					   struct ctl_table *table)

+{

+	if (!*ppos)

+		return false;

+

+	switch (sysctl_writes_strict) {

+	case SYSCTL_WRITES_STRICT:

+		return true;

+	case SYSCTL_WRITES_WARN:

+		warn_sysctl_write(table);

+		return false;

+	default:

+		return false;

+	}

+}

+

+/**

  * proc_dostring - read a string sysctl

  * @table: the sysctl table

  * @write: %TRUE if this is a write to the sysctl file

@@ -1992,8 +2018,8 @@ static void warn_sysctl_write(struct ctl_table *table)

 int proc_dostring(struct ctl_table *table, int write,

 		  void __user *buffer, size_t *lenp, loff_t *ppos)

 {

-	if (write && *ppos && sysctl_writes_strict == SYSCTL_WRITES_WARN)

-		warn_sysctl_write(table);

+	if (write)

+		proc_first_pos_non_zero_ignore(ppos, table);

 	return _proc_do_string((char *)(table->data), table->maxlen, write,

 			       (char __user *)buffer, lenp, ppos);

@@ -2195,17 +2221,8 @@ static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table,

 		conv = do_proc_dointvec_conv;

 	if (write) {

-		if (*ppos) {

-			switch (sysctl_writes_strict) {

-			case SYSCTL_WRITES_STRICT:

-				goto out;

-			case SYSCTL_WRITES_WARN:

-				warn_sysctl_write(table);

-				break;

-			default:

-				break;

-			}

-		}

+		if (proc_first_pos_non_zero_ignore(ppos, table))

+			goto out;

 		if (left > PAGE_SIZE - 1)

 			left = PAGE_SIZE - 1;

@@ -2480,17 +2497,8 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int

 	left = *lenp;

 	if (write) {

-		if (*ppos) {

-			switch (sysctl_writes_strict) {

-			case SYSCTL_WRITES_STRICT:

-				goto out;

-			case SYSCTL_WRITES_WARN:

-				warn_sysctl_write(table);

-				break;

-			default:

-				break;

-			}

-		}

+		if (proc_first_pos_non_zero_ignore(ppos, table))

+			goto out;

 		if (left > PAGE_SIZE - 1)

 			left = PAGE_SIZE - 1;

-- 

2.11.0