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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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14
arch/x86/include/asm/uaccess.h
View File

@@ -12,18 +12,6 @@
#include <asm/smap.h>
#include <asm/extable.h>
/*
* Test whether a block of memory is a valid user space address.
* Returns 0 if the range is valid, nonzero otherwise.
*/
static inline bool __access_ok(void __user *ptr, unsigned long size)
{
unsigned long limit = TASK_SIZE_MAX;
unsigned long addr = ptr;
return (size <= limit) && (addr <= (limit - size));
}
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
static inline bool pagefault_disabled(void);
# define WARN_ON_IN_IRQ() \
@@ -55,6 +43,8 @@ static inline bool pagefault_disabled(void);
likely(__access_ok(addr, size)); \
})
#include <asm-generic/access_ok.h>
extern int __get_user_1(void);
extern int __get_user_2(void);
extern int __get_user_4(void);