net: add a new sockptr_t type

Add a uptr_t type that can hold a pointer to either a user or kernel
memory region, and simply helpers to copy to and from it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Christoph Hellwig 2020-07-23 08:08:46 +02:00 committed by David S. Miller
parent d200cf624c
commit ba423fdaa5

104
include/linux/sockptr.h Normal file
View file

@ -0,0 +1,104 @@
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (c) 2020 Christoph Hellwig.
*
* Support for "universal" pointers that can point to either kernel or userspace
* memory.
*/
#ifndef _LINUX_SOCKPTR_H
#define _LINUX_SOCKPTR_H
#include <linux/slab.h>
#include <linux/uaccess.h>
typedef struct {
union {
void *kernel;
void __user *user;
};
bool is_kernel : 1;
} sockptr_t;
static inline bool sockptr_is_kernel(sockptr_t sockptr)
{
return sockptr.is_kernel;
}
static inline sockptr_t KERNEL_SOCKPTR(void *p)
{
return (sockptr_t) { .kernel = p, .is_kernel = true };
}
static inline sockptr_t USER_SOCKPTR(void __user *p)
{
return (sockptr_t) { .user = p };
}
static inline bool sockptr_is_null(sockptr_t sockptr)
{
return !sockptr.user && !sockptr.kernel;
}
static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
{
if (!sockptr_is_kernel(src))
return copy_from_user(dst, src.user, size);
memcpy(dst, src.kernel, size);
return 0;
}
static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
{
if (!sockptr_is_kernel(dst))
return copy_to_user(dst.user, src, size);
memcpy(dst.kernel, src, size);
return 0;
}
static inline void *memdup_sockptr(sockptr_t src, size_t len)
{
void *p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
if (!p)
return ERR_PTR(-ENOMEM);
if (copy_from_sockptr(p, src, len)) {
kfree(p);
return ERR_PTR(-EFAULT);
}
return p;
}
static inline void *memdup_sockptr_nul(sockptr_t src, size_t len)
{
char *p = kmalloc_track_caller(len + 1, GFP_KERNEL);
if (!p)
return ERR_PTR(-ENOMEM);
if (copy_from_sockptr(p, src, len)) {
kfree(p);
return ERR_PTR(-EFAULT);
}
p[len] = '\0';
return p;
}
static inline void sockptr_advance(sockptr_t sockptr, size_t len)
{
if (sockptr_is_kernel(sockptr))
sockptr.kernel += len;
else
sockptr.user += len;
}
static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
{
if (sockptr_is_kernel(src)) {
size_t len = min(strnlen(src.kernel, count - 1) + 1, count);
memcpy(dst, src.kernel, len);
return len;
}
return strncpy_from_user(dst, src.user, count);
}
#endif /* _LINUX_SOCKPTR_H */