linux/lib/usercopy.c
Arnd Bergmann 1f9a8286bc uaccess: always export _copy_[from|to]_user with CONFIG_RUST
Rust code needs to be able to access _copy_from_user and _copy_to_user
so that it can skip the check_copy_size check in cases where the length
is known at compile-time, mirroring the logic for when C code will skip
check_copy_size. To do this, we ensure that exported versions of these
methods are available when CONFIG_RUST is enabled.

Alice has verified that this patch passes the CONFIG_TEST_USER_COPY test
on x86 using the Android cuttlefish emulator.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/r/20240528-alice-mm-v7-2-78222c31b8f4@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2024-07-08 23:44:01 +02:00

84 lines
2.1 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/fault-inject-usercopy.h>
#include <linux/instrumented.h>
#include <linux/kernel.h>
#include <linux/nospec.h>
#include <linux/string.h>
#include <linux/uaccess.h>
#include <linux/wordpart.h>
/* out-of-line parts */
#if !defined(INLINE_COPY_FROM_USER) || defined(CONFIG_RUST)
unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
{
return _inline_copy_from_user(to, from, n);
}
EXPORT_SYMBOL(_copy_from_user);
#endif
#if !defined(INLINE_COPY_TO_USER) || defined(CONFIG_RUST)
unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
{
return _inline_copy_to_user(to, from, n);
}
EXPORT_SYMBOL(_copy_to_user);
#endif
/**
* check_zeroed_user: check if a userspace buffer only contains zero bytes
* @from: Source address, in userspace.
* @size: Size of buffer.
*
* This is effectively shorthand for "memchr_inv(from, 0, size) == NULL" for
* userspace addresses (and is more efficient because we don't care where the
* first non-zero byte is).
*
* Returns:
* * 0: There were non-zero bytes present in the buffer.
* * 1: The buffer was full of zero bytes.
* * -EFAULT: access to userspace failed.
*/
int check_zeroed_user(const void __user *from, size_t size)
{
unsigned long val;
uintptr_t align = (uintptr_t) from % sizeof(unsigned long);
if (unlikely(size == 0))
return 1;
from -= align;
size += align;
if (!user_read_access_begin(from, size))
return -EFAULT;
unsafe_get_user(val, (unsigned long __user *) from, err_fault);
if (align)
val &= ~aligned_byte_mask(align);
while (size > sizeof(unsigned long)) {
if (unlikely(val))
goto done;
from += sizeof(unsigned long);
size -= sizeof(unsigned long);
unsafe_get_user(val, (unsigned long __user *) from, err_fault);
}
if (size < sizeof(unsigned long))
val &= aligned_byte_mask(size);
done:
user_read_access_end();
return (val == 0);
err_fault:
user_read_access_end();
return -EFAULT;
}
EXPORT_SYMBOL(check_zeroed_user);