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When opening user access to only perform reads, only open read access. When opening user access to only perform writes, only open write access. Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/2e73bc57125c2c6ab12a587586a4eed3a47105fc.1585898438.git.christophe.leroy@c-s.fr
89 lines
2.0 KiB
C
89 lines
2.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/uaccess.h>
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#include <linux/bitops.h>
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/* out-of-line parts */
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#ifndef INLINE_COPY_FROM_USER
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unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
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{
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unsigned long res = n;
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might_fault();
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if (likely(access_ok(from, n))) {
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kasan_check_write(to, n);
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res = raw_copy_from_user(to, from, n);
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}
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if (unlikely(res))
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memset(to + (n - res), 0, res);
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return res;
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}
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EXPORT_SYMBOL(_copy_from_user);
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#endif
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#ifndef INLINE_COPY_TO_USER
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unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
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{
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might_fault();
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if (likely(access_ok(to, n))) {
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kasan_check_read(from, n);
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n = raw_copy_to_user(to, from, n);
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}
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return n;
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}
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EXPORT_SYMBOL(_copy_to_user);
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#endif
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/**
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* check_zeroed_user: check if a userspace buffer only contains zero bytes
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* @from: Source address, in userspace.
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* @size: Size of buffer.
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*
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* This is effectively shorthand for "memchr_inv(from, 0, size) == NULL" for
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* userspace addresses (and is more efficient because we don't care where the
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* first non-zero byte is).
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*
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* Returns:
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* * 0: There were non-zero bytes present in the buffer.
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* * 1: The buffer was full of zero bytes.
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* * -EFAULT: access to userspace failed.
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*/
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int check_zeroed_user(const void __user *from, size_t size)
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{
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unsigned long val;
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uintptr_t align = (uintptr_t) from % sizeof(unsigned long);
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if (unlikely(size == 0))
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return 1;
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from -= align;
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size += align;
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if (!user_read_access_begin(from, size))
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return -EFAULT;
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unsafe_get_user(val, (unsigned long __user *) from, err_fault);
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if (align)
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val &= ~aligned_byte_mask(align);
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while (size > sizeof(unsigned long)) {
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if (unlikely(val))
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goto done;
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from += sizeof(unsigned long);
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size -= sizeof(unsigned long);
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unsafe_get_user(val, (unsigned long __user *) from, err_fault);
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}
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if (size < sizeof(unsigned long))
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val &= aligned_byte_mask(size);
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done:
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user_read_access_end();
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return (val == 0);
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err_fault:
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user_read_access_end();
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return -EFAULT;
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}
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EXPORT_SYMBOL(check_zeroed_user);
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