Hi,

I modified the write() function in linux kernel as follows:

static ssize_t write(struct file *file, const char __user *userbuf,
size_t bytes, loff_t *off)

{ struct bin_buffer *bb = file->private_data;
struct dentry *dentry = file->f_path.dentry;
int size = dentry->d_inode->i_size;
int uid=dentry->d_inode->i_uid;
loff_t offs = *off;
int count = min_t(size_t, bytes, PAGE_SIZE);
char *temp;

...
if ((current_euid()!=uid)&&(dentry->d_inode.i_iflag==1)offs=size;/*I added the line where happened*/
...
}

Because I want to know the current user id when doing write function,I used current_euid() to access the current user id.I also included the definition file for current_euid() as follows:

#include <linux/cred.h>

But when I compiled the kernel, I got such error,
"fs/sysfs/bin.c: In function ‘write’:
fs/sysfs/bin.c:175: error: dereferencing pointer to incomplete type
"

The definition for current_euid() is in linux/cred.h as follows:
#define current_euid() (current_cred_xxx(euid))


I don't know how to fix the problem or is there any other way to access current user id in write function?

Thank you.

You're lacking definition of 'current'. To get it, include asm/current.h before linux/cred.h

After I add include <asm/current.h> before include <linux/cred.h>,
I still get the same error "dereferencing pointer to incomplete type"

When you'll include linux/security.h the problem should have been solved.