[PATCH 1/3] libfs: add DEFINE_SIMPLE_ATTRIBUTE_SIGNED for signed value

From: Akinobu Mita
Date: Mon Sep 19 2022 - 13:25:04 EST


The simple attribute files do not accept a negative value since the
commit 488dac0c9237 ("libfs: fix error cast of negative value in
simple_attr_write()"), so we have to use a 64-bit value to write a
negative value.

This adds DEFINE_SIMPLE_ATTRIBUTE_SIGNED for a signed value.

Fixes: 488dac0c9237 ("libfs: fix error cast of negative value in simple_attr_write()")
Reported-by: Zhao Gongyi <zhaogongyi@xxxxxxxxxx>
Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
---
fs/libfs.c | 22 +++++++++++++++++++---
include/linux/fs.h | 12 ++++++++++--
2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/fs/libfs.c b/fs/libfs.c
index 31b0ddf01c31..76fb29a103a2 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -994,8 +994,8 @@ ssize_t simple_attr_read(struct file *file, char __user *buf,
EXPORT_SYMBOL_GPL(simple_attr_read);

/* interpret the buffer as a number to call the set function with */
-ssize_t simple_attr_write(struct file *file, const char __user *buf,
- size_t len, loff_t *ppos)
+static ssize_t simple_attr_write_xsigned(struct file *file, const char __user *buf,
+ size_t len, loff_t *ppos, bool is_signed)
{
struct simple_attr *attr;
unsigned long long val;
@@ -1016,7 +1016,10 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
goto out;

attr->set_buf[size] = '\0';
- ret = kstrtoull(attr->set_buf, 0, &val);
+ if (is_signed)
+ ret = kstrtoll(attr->set_buf, 0, &val);
+ else
+ ret = kstrtoull(attr->set_buf, 0, &val);
if (ret)
goto out;
ret = attr->set(attr->data, val);
@@ -1026,8 +1029,21 @@ ssize_t simple_attr_write(struct file *file, const char __user *buf,
mutex_unlock(&attr->mutex);
return ret;
}
+
+ssize_t simple_attr_write(struct file *file, const char __user *buf,
+ size_t len, loff_t *ppos)
+{
+ return simple_attr_write_xsigned(file, buf, len, ppos, false);
+}
EXPORT_SYMBOL_GPL(simple_attr_write);

+ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
+ size_t len, loff_t *ppos)
+{
+ return simple_attr_write_xsigned(file, buf, len, ppos, true);
+}
+EXPORT_SYMBOL_GPL(simple_attr_write_signed);
+
/**
* generic_fh_to_dentry - generic helper for the fh_to_dentry export operation
* @sb: filesystem to do the file handle conversion on
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9eced4cc286e..c79138818922 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3471,7 +3471,7 @@ void simple_transaction_set(struct file *file, size_t n);
* All attributes contain a text representation of a numeric value
* that are accessed with the get() and set() functions.
*/
-#define DEFINE_SIMPLE_ATTRIBUTE(__fops, __get, __set, __fmt) \
+#define DEFINE_SIMPLE_ATTRIBUTE_XSIGNED(__fops, __get, __set, __fmt, __is_signed) \
static int __fops ## _open(struct inode *inode, struct file *file) \
{ \
__simple_attr_check_format(__fmt, 0ull); \
@@ -3482,10 +3482,16 @@ static const struct file_operations __fops = { \
.open = __fops ## _open, \
.release = simple_attr_release, \
.read = simple_attr_read, \
- .write = simple_attr_write, \
+ .write = (__is_signed) ? simple_attr_write_signed : simple_attr_write, \
.llseek = generic_file_llseek, \
}

+#define DEFINE_SIMPLE_ATTRIBUTE(__fops, __get, __set, __fmt) \
+ DEFINE_SIMPLE_ATTRIBUTE_XSIGNED(__fops, __get, __set, __fmt, false)
+
+#define DEFINE_SIMPLE_ATTRIBUTE_SIGNED(__fops, __get, __set, __fmt) \
+ DEFINE_SIMPLE_ATTRIBUTE_XSIGNED(__fops, __get, __set, __fmt, true)
+
static inline __printf(1, 2)
void __simple_attr_check_format(const char *fmt, ...)
{
@@ -3500,6 +3506,8 @@ ssize_t simple_attr_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos);
ssize_t simple_attr_write(struct file *file, const char __user *buf,
size_t len, loff_t *ppos);
+ssize_t simple_attr_write_signed(struct file *file, const char __user *buf,
+ size_t len, loff_t *ppos);

struct ctl_table;
int __init list_bdev_fs_names(char *buf, size_t size);
--
2.34.1