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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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5
arch/um/include/asm/uaccess.h
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@@ -25,7 +25,7 @@
extern unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n);
extern unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n);
extern unsigned long __clear_user(void __user *mem, unsigned long len);
static inline int __access_ok(unsigned long addr, unsigned long size);
static inline int __access_ok(const void __user *ptr, unsigned long size);
/* Teach asm-generic/uaccess.h that we have C functions for these. */
#define __access_ok __access_ok
@@ -36,8 +36,9 @@ static inline int __access_ok(unsigned long addr, unsigned long size);
#include <asm-generic/uaccess.h>
static inline int __access_ok(unsigned long addr, unsigned long size)
static inline int __access_ok(const void __user *ptr, unsigned long size)
{
unsigned long addr = (unsigned long)ptr;
return __addr_range_nowrap(addr, size) &&
(__under_task_size(addr, size) ||
__access_ok_vsyscall(addr, size));