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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 /kernel/exit.c
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 'kernel/exit.c')
-rw-r--r--kernel/exit.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 8a01b671dc1f..2d14979577ee 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1604,10 +1604,9 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
if (!infop)
return err;
- if (!access_ok(infop, sizeof(*infop)))
+ if (!user_access_begin(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);
@@ -1732,10 +1731,9 @@ COMPAT_SYSCALL_DEFINE5(waitid,
if (!infop)
return err;
- if (!access_ok(infop, sizeof(*infop)))
+ if (!user_access_begin(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);