linux/mm/maccess.c
Christoph Hellwig 7676fbf21b maccess: remove strncpy_from_unsafe
All users are gone now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200521152301.2587579-16-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-09 09:39:15 -07:00

273 lines
7.3 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Access kernel or user memory without faulting.
*/
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
static long __probe_kernel_read(void *dst, const void *src, size_t size,
bool strict);
bool __weak probe_kernel_read_allowed(const void *unsafe_src, size_t size,
bool strict)
{
return true;
}
/**
* probe_kernel_read(): safely attempt to read from any location
* @dst: pointer to the buffer that shall take the data
* @src: address to read from
* @size: size of the data chunk
*
* Same as probe_kernel_read_strict() except that for architectures with
* not fully separated user and kernel address spaces this function also works
* for user address tanges.
*
* DO NOT USE THIS FUNCTION - it is broken on architectures with entirely
* separate kernel and user address spaces, and also a bad idea otherwise.
*/
long probe_kernel_read(void *dst, const void *src, size_t size)
{
return __probe_kernel_read(dst, src, size, false);
}
EXPORT_SYMBOL_GPL(probe_kernel_read);
/**
* probe_kernel_read_strict(): safely attempt to read from kernel-space
* @dst: pointer to the buffer that shall take the data
* @src: address to read from
* @size: size of the data chunk
*
* Safely read from kernel address @src to the buffer at @dst. If a kernel
* fault happens, handle that and return -EFAULT.
*
* We ensure that the copy_from_user is executed in atomic context so that
* do_page_fault() doesn't attempt to take mmap_lock. This makes
* probe_kernel_read() suitable for use within regions where the caller
* already holds mmap_lock, or other locks which nest inside mmap_lock.
*/
long probe_kernel_read_strict(void *dst, const void *src, size_t size)
{
return __probe_kernel_read(dst, src, size, true);
}
static long __probe_kernel_read(void *dst, const void *src, size_t size,
bool strict)
{
long ret;
mm_segment_t old_fs = get_fs();
if (!probe_kernel_read_allowed(src, size, strict))
return -EFAULT;
set_fs(KERNEL_DS);
pagefault_disable();
ret = __copy_from_user_inatomic(dst, (__force const void __user *)src,
size);
pagefault_enable();
set_fs(old_fs);
if (ret)
return -EFAULT;
return 0;
}
/**
* probe_user_read(): safely attempt to read from a user-space location
* @dst: pointer to the buffer that shall take the data
* @src: address to read from. This must be a user address.
* @size: size of the data chunk
*
* Safely read from user address @src to the buffer at @dst. If a kernel fault
* happens, handle that and return -EFAULT.
*/
long probe_user_read(void *dst, const void __user *src, size_t size)
{
long ret = -EFAULT;
mm_segment_t old_fs = get_fs();
set_fs(USER_DS);
if (access_ok(src, size)) {
pagefault_disable();
ret = __copy_from_user_inatomic(dst, src, size);
pagefault_enable();
}
set_fs(old_fs);
if (ret)
return -EFAULT;
return 0;
}
EXPORT_SYMBOL_GPL(probe_user_read);
/**
* probe_kernel_write(): safely attempt to write to a location
* @dst: address to write to
* @src: pointer to the data that shall be written
* @size: size of the data chunk
*
* Safely write to address @dst from the buffer at @src. If a kernel fault
* happens, handle that and return -EFAULT.
*/
long probe_kernel_write(void *dst, const void *src, size_t size)
{
long ret;
mm_segment_t old_fs = get_fs();
set_fs(KERNEL_DS);
pagefault_disable();
ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
pagefault_enable();
set_fs(old_fs);
if (ret)
return -EFAULT;
return 0;
}
/**
* probe_user_write(): safely attempt to write to a user-space location
* @dst: address to write to
* @src: pointer to the data that shall be written
* @size: size of the data chunk
*
* Safely write to address @dst from the buffer at @src. If a kernel fault
* happens, handle that and return -EFAULT.
*/
long probe_user_write(void __user *dst, const void *src, size_t size)
{
long ret = -EFAULT;
mm_segment_t old_fs = get_fs();
set_fs(USER_DS);
if (access_ok(dst, size)) {
pagefault_disable();
ret = __copy_to_user_inatomic(dst, src, size);
pagefault_enable();
}
set_fs(old_fs);
if (ret)
return -EFAULT;
return 0;
}
EXPORT_SYMBOL_GPL(probe_user_write);
/**
* strncpy_from_kernel_nofault: - Copy a NUL terminated string from unsafe
* address.
* @dst: Destination address, in kernel space. This buffer must be at
* least @count bytes long.
* @unsafe_addr: Unsafe address.
* @count: Maximum number of bytes to copy, including the trailing NUL.
*
* Copies a NUL-terminated string from unsafe address to kernel buffer.
*
* On success, returns the length of the string INCLUDING the trailing NUL.
*
* If access fails, returns -EFAULT (some data may have been copied
* and the trailing NUL added).
*
* If @count is smaller than the length of the string, copies @count-1 bytes,
* sets the last byte of @dst buffer to NUL and returns @count.
*/
long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
{
mm_segment_t old_fs = get_fs();
const void *src = unsafe_addr;
long ret;
if (unlikely(count <= 0))
return 0;
if (!probe_kernel_read_allowed(unsafe_addr, count, true))
return -EFAULT;
set_fs(KERNEL_DS);
pagefault_disable();
do {
ret = __get_user(*dst++, (const char __user __force *)src++);
} while (dst[-1] && ret == 0 && src - unsafe_addr < count);
dst[-1] = '\0';
pagefault_enable();
set_fs(old_fs);
return ret ? -EFAULT : src - unsafe_addr;
}
/**
* strncpy_from_user_nofault: - Copy a NUL terminated string from unsafe user
* address.
* @dst: Destination address, in kernel space. This buffer must be at
* least @count bytes long.
* @unsafe_addr: Unsafe user address.
* @count: Maximum number of bytes to copy, including the trailing NUL.
*
* Copies a NUL-terminated string from unsafe user address to kernel buffer.
*
* On success, returns the length of the string INCLUDING the trailing NUL.
*
* If access fails, returns -EFAULT (some data may have been copied
* and the trailing NUL added).
*
* If @count is smaller than the length of the string, copies @count-1 bytes,
* sets the last byte of @dst buffer to NUL and returns @count.
*/
long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
long count)
{
mm_segment_t old_fs = get_fs();
long ret;
if (unlikely(count <= 0))
return 0;
set_fs(USER_DS);
pagefault_disable();
ret = strncpy_from_user(dst, unsafe_addr, count);
pagefault_enable();
set_fs(old_fs);
if (ret >= count) {
ret = count;
dst[ret - 1] = '\0';
} else if (ret > 0) {
ret++;
}
return ret;
}
/**
* strnlen_user_nofault: - Get the size of a user string INCLUDING final NUL.
* @unsafe_addr: The string to measure.
* @count: Maximum count (including NUL)
*
* Get the size of a NUL-terminated string in user space without pagefault.
*
* Returns the size of the string INCLUDING the terminating NUL.
*
* If the string is too long, returns a number larger than @count. User
* has to check the return value against "> count".
* On exception (or invalid count), returns 0.
*
* Unlike strnlen_user, this can be used from IRQ handler etc. because
* it disables pagefaults.
*/
long strnlen_user_nofault(const void __user *unsafe_addr, long count)
{
mm_segment_t old_fs = get_fs();
int ret;
set_fs(USER_DS);
pagefault_disable();
ret = strnlen_user(unsafe_addr, count);
pagefault_enable();
set_fs(old_fs);
return ret;
}