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uaccess: generalize access_ok()

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There are many different ways that access_ok() is defined across
architectures, but in the end, they all just compare against the
user_addr_max() value or they accept anything.

Provide one definition that works for most architectures, checking
against TASK_SIZE_MAX for user processes or skipping the check inside
of uaccess_kernel() sections.

For architectures without CONFIG_SET_FS(), this should be the fastest
check, as it comes down to a single comparison of a pointer against a
compile-time constant, while the architecture specific versions tend to
do something more complex for historic reasons or get something wrong.

Type checking for __user annotations is handled inconsistently across
architectures, but this is easily simplified as well by using an inline
function that takes a 'const void __user *' argument. A handful of
callers need an extra __user annotation for this.

Some architectures had trick to use 33-bit or 65-bit arithmetic on the
addresses to calculate the overflow, however this simpler version uses
fewer registers, which means it can produce better object code in the
end despite needing a second (statically predicted) branch.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mark Rutland <mark.rutland@arm.com> [arm64, asm-generic]
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Stafford Horne <shorne@gmail.com>
Acked-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Arnd Bergmann
2022-02-15 17:55:04 +01:00
parent 23fc539e81
commit 12700c17fc
32 changed files with 110 additions and 362 deletions
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19
arch/openrisc/include/asm/uaccess.h
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@@ -45,21 +45,7 @@
#define uaccess_kernel() (get_fs() == KERNEL_DS)
/* Ensure that the range from addr to addr+size is all within the process'
* address space
*/
static inline int __range_ok(unsigned long addr, unsigned long size)
{
const mm_segment_t fs = get_fs();
return size <= fs && addr <= (fs - size);
}
#define access_ok(addr, size) \
({ \
__chk_user_ptr(addr); \
__range_ok((unsigned long)(addr), (size)); \
})
#include <asm-generic/access_ok.h>
/*
* These are the main single-value transfer routines. They automatically
@@ -268,9 +254,6 @@ clear_user(void __user *addr, unsigned long size)
return size;
}
#define user_addr_max() \
(uaccess_kernel() ? ~0UL : TASK_SIZE)
extern long strncpy_from_user(char *dest, const char __user *src, long count);
extern __must_check long strnlen_user(const char __user *str, long n);