waitid(): Add missing access_ok() checks

Adds missing access_ok() checks.

CVE-2017-5123

Reported-by: Chris Salls <chrissalls5@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Fixes: 4c48abe91be0 ("waitid(): switch copyout of siginfo to unsafe_put_user()")
Cc: stable@kernel.org # 4.13
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index f2cd53e92147..cf28528842bc 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1610,6 +1610,9 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
         if (!infop)
                 return err;
 
+        if (!access_ok(VERIFY_WRITE, infop, sizeof(*infop)))
+                goto Efault;
+
         user_access_begin();
         unsafe_put_user(signo, &infop->si_signo, Efault);
         unsafe_put_user(0, &infop->si_errno, Efault);
@@ -1735,6 +1738,9 @@ COMPAT_SYSCALL_DEFINE5(waitid,
         if (!infop)
                 return err;
 
+        if (!access_ok(VERIFY_WRITE, infop, sizeof(*infop)))
+                goto Efault;
+
         user_access_begin();
         unsafe_put_user(signo, &infop->si_signo, Efault);
         unsafe_put_user(0, &infop->si_errno, Efault);