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authorLinus Torvalds <torvalds@linux-foundation.org>2019-01-04 12:56:09 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-04 12:56:09 -0800
commit594cc251fdd0d231d342d88b2fdff4bc42fb0690 (patch)
tree259269a399e6504a7cf8739201cf172d1cbb197a /include
parent0b2c8f8b6b0c7530e2866c95862546d0da2057b0 (diff)
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.h2
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)