diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-01-04 12:56:09 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-06-22 09:04:58 +0200 |
| commit | 216284c4a126b28469eb0bf4994c669e251f47ba (patch) | |
| tree | 2b454ee3dc77dee76acd2792159cf8e71716d83a /kernel/exit.c | |
| parent | 6f89ad2e79c3d67b8390d74666225b7489e3f280 (diff) | |
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 'kernel/exit.c')
| -rw-r--r-- | kernel/exit.c | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 54c3269b8dda..894fca56a38c 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1617,10 +1617,9 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *, if (!infop) return err; - if (!access_ok(VERIFY_WRITE, infop, sizeof(*infop))) + if (!user_access_begin(VERIFY_WRITE, infop, sizeof(*infop))) return -EFAULT; - user_access_begin(); unsafe_put_user(signo, &infop->si_signo, Efault); unsafe_put_user(0, &infop->si_errno, Efault); unsafe_put_user(info.cause, &infop->si_code, Efault); @@ -1745,10 +1744,9 @@ COMPAT_SYSCALL_DEFINE5(waitid, if (!infop) return err; - if (!access_ok(VERIFY_WRITE, infop, sizeof(*infop))) + if (!user_access_begin(VERIFY_WRITE, infop, sizeof(*infop))) return -EFAULT; - user_access_begin(); unsafe_put_user(signo, &infop->si_signo, Efault); unsafe_put_user(0, &infop->si_errno, Efault); unsafe_put_user(info.cause, &infop->si_code, Efault); |