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new primitive: vmemdup_user() 

similar to memdup_user(), but does *not* guarantee that result will
be physically contiguous; use only in cases where that's not a requirement
and free it with kvfree().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2018-01-07 13:06:15 -05:00
parent 6c2c97a24f
commit 50fd2f298b
2 changed files with 29 additions and 1 deletions
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1
include/linux/string.h
View File

@ -11,6 +11,7 @@
extern char *strndup_user(const char __user *, long);
extern void *memdup_user(const void __user *, size_t);
extern void *vmemdup_user(const void __user *, size_t);
extern void *memdup_user_nul(const void __user *, size_t);
/*

29
mm/util.c
View File

@ -150,7 +150,8 @@ EXPORT_SYMBOL(kmemdup_nul);
* @src: source address in user space
* @len: number of bytes to copy
*
* Returns an ERR_PTR() on failure.
* Returns an ERR_PTR() on failure. Result is physically
* contiguous, to be freed by kfree().
*/
void *memdup_user(const void __user *src, size_t len)
{
@ -169,6 +170,32 @@ void *memdup_user(const void __user *src, size_t len)
}
EXPORT_SYMBOL(memdup_user);
/**
* vmemdup_user - duplicate memory region from user space
*
* @src: source address in user space
* @len: number of bytes to copy
*
* Returns an ERR_PTR() on failure. Result may be not
* physically contiguous. Use kvfree() to free.
*/
void *vmemdup_user(const void __user *src, size_t len)
{
void *p;
p = kvmalloc(len, GFP_USER);
if (!p)
return ERR_PTR(-ENOMEM);
if (copy_from_user(p, src, len)) {
kvfree(p);
return ERR_PTR(-EFAULT);
}
return p;
}
EXPORT_SYMBOL(vmemdup_user);
/*
* strndup_user - duplicate an existing string from user space
* @s: The string to duplicate