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authorLinus Torvalds <torvalds@linux-foundation.org>2019-01-04 21:56:09 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-04 21:56:09 +0100
commit594cc251fdd0d231d342d88b2fdff4bc42fb0690 (patch)
tree259269a399e6504a7cf8739201cf172d1cbb197a /lib/audit.c
parenti915: fix missing user_access_end() in page fault exception case (diff)
downloadlinux-594cc251fdd0d231d342d88b2fdff4bc42fb0690.tar.xz
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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 'lib/audit.c')
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