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uaccess: add generic __{get,put}_kernel_nofault

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Nine architectures are still missing __{get,put}_kernel_nofault:
alpha, ia64, microblaze, nds32, nios2, openrisc, sh, sparc32, xtensa.

Add a generic version that lets everything use the normal
copy_{from,to}_kernel_nofault() code based on these, removing the last
use of get_fs()/set_fs() from architecture-independent code.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Arnd Bergmann
2022-02-11 08:50:00 +01:00
parent 90997c1280
commit 34737e2698
14 changed files with 19 additions and 131 deletions
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108
mm/maccess.c
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@@ -12,8 +12,6 @@ bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
return true;
}
#ifdef HAVE_GET_KERNEL_NOFAULT
#define copy_from_kernel_nofault_loop(dst, src, len, type, err_label) \
while (len >= sizeof(type)) { \
__get_kernel_nofault(dst, src, type, err_label); \
@@ -102,112 +100,6 @@ Efault:
dst[-1] = '\0';
return -EFAULT;
}
#else /* HAVE_GET_KERNEL_NOFAULT */
/**
* copy_from_kernel_nofault(): 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. If @src is not a valid kernel
* address, return -ERANGE.
*
* 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
* copy_from_kernel_nofault() suitable for use within regions where the caller
* already holds mmap_lock, or other locks which nest inside mmap_lock.
*/
long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
{
long ret;
mm_segment_t old_fs = get_fs();
if (!copy_from_kernel_nofault_allowed(src, size))
return -ERANGE;
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;
}
EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);
/**
* copy_to_kernel_nofault(): 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 copy_to_kernel_nofault(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;
}
/**
* 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 @unsafe_addr is not a valid kernel address, return
* -ERANGE.
*
* 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 (!copy_from_kernel_nofault_allowed(unsafe_addr, count))
return -ERANGE;
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;
}
#endif /* HAVE_GET_KERNEL_NOFAULT */
/**
* copy_from_user_nofault(): safely attempt to read from a user-space location