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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-01-04 12:56:09 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-06-20 10:24:58 +0200 |
| commit | b25df2918ba94ccc0ae44b4bb53f0f76a4bb0e96 (patch) | |
| tree | 57bfb157e9e736b7f1f7dd6d2b830d885bf96c84 /arch/x86/include | |
| parent | b5bad1d50146d4bca460c876aec5863c3d0506b8 (diff) | |
| download | linux-rt-b25df2918ba94ccc0ae44b4bb53f0f76a4bb0e96.tar.gz | |
make 'user_access_begin()' do 'access_ok()'
commit 594cc251fdd0d231d342d88b2fdff4bc42fb0690 upstream.
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>
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/uaccess.h | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 971830341061..d871e424fa50 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -711,7 +711,17 @@ 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(int type, + const void __user *ptr, + size_t len) +{ + if (unlikely(!access_ok(type, ptr, len))) + return 0; + __uaccess_begin(); + return 1; +} + +#define user_access_begin(a, b, c) user_access_begin(a, b, c) #define user_access_end() __uaccess_end() #define unsafe_put_user(x, ptr, err_label) \ |