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ARM: make user_addr_max more robust 

With CONFIG_MMU=y get_fs() returns current_thread_info()->addr_limit
which is initialized as USER_DS (which in turn is defined to TASK_SIZE)
for userspace processes. At least theoretically
current_thread_info()->addr_limit is changable by set_fs() to a
different limit, so checking for KERNEL_DS is more robust.

With !CONFIG_MMU get_fs returns KERNEL_DS. To see what the old variant
did you'd have to find out that USER_DS == KERNEL_DS which isn't needed
any more with the variant this patch introduces. So it's a bit easier to
understand, too.

Also if the limit was changed this limit should be returned, not
TASK_SIZE.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
This commit is contained in:
Uwe Kleine-König 2014-06-05 10:23:10 +02:00
parent 03eca20006
commit 83de911cf8
1 changed files with 1 additions and 1 deletions
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2
arch/arm/include/asm/uaccess.h
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@ -224,7 +224,7 @@ static inline void set_fs(mm_segment_t fs)
#define access_ok(type,addr,size) (__range_ok(addr,size) == 0)
#define user_addr_max() \
(segment_eq(get_fs(), USER_DS) ? TASK_SIZE : ~0UL)
(segment_eq(get_fs(), KERNEL_DS) ? ~0UL : get_fs())
/*
* The "__xxx" versions of the user access functions do not verify the