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| author |   Linus Torvalds <torvalds@linux-foundation.org> | 2019-01-04 12:56:09 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-01-04 12:56:09 -0800 |
| commit | 594cc251fdd0d231d342d88b2fdff4bc42fb0690 (patch) | |
| tree | 259269a399e6504a7cf8739201cf172d1cbb197a /include | |
| parent | i915: fix missing user_access_end() in page fault exception case (diff) | |
| download | linux-dev-594cc251fdd0d231d342d88b2fdff4bc42fb0690.tar.xz linux-dev-594cc251fdd0d231d342d88b2fdff4bc42fb0690.zip | |
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 'include')
| -rw-r--r-- | include/linux/uaccess.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index bf2523867a02..37b226e8df13 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -264,7 +264,7 @@ extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count); probe_kernel_read(&retval, addr, sizeof(retval)) #ifndef user_access_begin -#define user_access_begin() do { } while (0) +#define user_access_begin(ptr,len) access_ok(ptr, len) #define user_access_end() do { } while (0) #define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0) #define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0) |