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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-01-04 23:56:09 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-01-04 23:56:09 +0300 |
| commit | 594cc251fdd0d231d342d88b2fdff4bc42fb0690 (patch) | |
| tree | 259269a399e6504a7cf8739201cf172d1cbb197a /arch | |
| parent | 0b2c8f8b6b0c7530e2866c95862546d0da2057b0 (diff) | |
| download | linux-594cc251fdd0d231d342d88b2fdff4bc42fb0690.tar.xz | |
make 'user_access_begin()' do 'access_ok()'
Originally, the rule used to be that you'd have to do access_ok()
separately, and then user_access_begin() before actually doing the
direct (optimized) user access.
But experience has shown that people then decide not to do access_ok()
at all, and instead rely on it being implied by other operations or
similar. Which makes it very hard to verify that the access has
actually been range-checked.
If you use the unsafe direct user accesses, hardware features (either
SMAP - Supervisor Mode Access Protection - on x86, or PAN - Privileged
Access Never - on ARM) do force you to use user_access_begin(). But
nothing really forces the range check.
By putting the range check into user_access_begin(), we actually force
people to do the right thing (tm), and the range check vill be visible
near the actual accesses. We have way too long a history of people
trying to avoid them.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/uaccess.h | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 3920f456db79..a87ab5290ab4 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -705,7 +705,14 @@ extern struct movsl_mask { * checking before using them, but you have to surround them with the * user_access_begin/end() pair. */ -#define user_access_begin() __uaccess_begin() +static __must_check inline bool user_access_begin(const void __user *ptr, size_t len) +{ + if (unlikely(!access_ok(ptr,len))) + return 0; + __uaccess_begin(); + return 1; +} +#define user_access_begin(a,b) user_access_begin(a,b) #define user_access_end() __uaccess_end() #define unsafe_put_user(x, ptr, err_label) \ |