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uaccess: add infrastructure for kernel builds with set_fs()

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Add a CONFIG_SET_FS option that is selected by architecturess that
implement set_fs, which is all of them initially.  If the option is not
set stubs for routines related to overriding the address space are
provided so that architectures can start to opt out of providing set_fs.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig
2020-09-03 16:22:35 +02:00
committed by Al Viro
parent 36e2c7421f
commit 5e6e9852d6
26 changed files with 45 additions and 0 deletions
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18
include/linux/uaccess.h
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@@ -8,6 +8,7 @@
#include <asm/uaccess.h>
#ifdef CONFIG_SET_FS
/*
* Force the uaccess routines to be wired up for actual userspace access,
* overriding any possible set_fs(KERNEL_DS) still lingering around. Undone
@@ -25,6 +26,23 @@ static inline void force_uaccess_end(mm_segment_t oldfs)
{
set_fs(oldfs);
}
#else /* CONFIG_SET_FS */
typedef struct {
/* empty dummy */
} mm_segment_t;
#define uaccess_kernel() (false)
#define user_addr_max() (TASK_SIZE_MAX)
static inline mm_segment_t force_uaccess_begin(void)
{
return (mm_segment_t) { };
}
static inline void force_uaccess_end(mm_segment_t oldfs)
{
}
#endif /* CONFIG_SET_FS */
/*
* Architectures should provide two primitives (raw_copy_{to,from}_user())