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authorDmitry Chagin <dchagin@FreeBSD.org>2021-06-10 11:23:11 +0000
committerMark Johnston <markj@FreeBSD.org>2021-06-29 18:47:53 +0000
commitf80ee27f447abc7baeb413cc0a7b7c21f9d32f8b (patch)
treebe225b32ec33d9673a8c2e23a6db0c4048e2ae5b
parent7bbd5ebae80b52a87d62164a04221752efa8fd50 (diff)
downloadsrc-f80ee27f447abc7baeb413cc0a7b7c21f9d32f8b.tar.gz
src-f80ee27f447abc7baeb413cc0a7b7c21f9d32f8b.zip
linux(4): Prevent integer overflow in futex_requeue.
To prevent a signed integer overflow in futex_requeue add a sanity check to catch negative values of nrwake or nrrequeue. (cherry picked from commit 25b09d6f398ea8a260ee8e2e8209fd76c61e13ee)
-rw-r--r--sys/compat/linux/linux_futex.c23
1 files changed, 16 insertions, 7 deletions
diff --git a/sys/compat/linux/linux_futex.c b/sys/compat/linux/linux_futex.c
index 686d2f7d2ec7..0be0483f4496 100644
--- a/sys/compat/linux/linux_futex.c
+++ b/sys/compat/linux/linux_futex.c
@@ -596,18 +596,19 @@ futex_wake(struct futex *f, int n, uint32_t bitset)
}
static int
-futex_requeue(struct futex *f, int n, struct futex *f2, int n2)
+futex_requeue(struct futex *f, int nrwake, struct futex *f2,
+ int nrrequeue)
{
struct waiting_proc *wp, *wpt;
int count = 0;
- LIN_SDT_PROBE4(futex, futex_requeue, entry, f, n, f2, n2);
+ LIN_SDT_PROBE4(futex, futex_requeue, entry, f, nrwake, f2, nrrequeue);
FUTEX_ASSERT_LOCKED(f);
FUTEX_ASSERT_LOCKED(f2);
TAILQ_FOREACH_SAFE(wp, &f->f_waiting_proc, wp_list, wpt) {
- if (++count <= n) {
+ if (++count <= nrwake) {
LINUX_CTR2(sys_futex, "futex_req_wake uaddr %p wp %p",
f->f_uaddr, wp);
wp->wp_flags |= FUTEX_WP_REMOVED;
@@ -633,7 +634,7 @@ futex_requeue(struct futex *f, int n, struct futex *f2, int n2)
FUTEXES_LOCK;
++f2->f_refcount;
FUTEXES_UNLOCK;
- if (count - n >= n2)
+ if (count - nrwake >= nrrequeue)
break;
}
}
@@ -744,7 +745,7 @@ futex_atomic_op(struct thread *td, int encoded_op, uint32_t *uaddr)
int
linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
{
- int clockrt, nrwake, op_ret, ret;
+ int clockrt, nrwake, nrrequeue, op_ret, ret;
struct linux_pemuldata *pem;
struct waiting_proc *wp;
struct futex *f, *f2;
@@ -888,6 +889,15 @@ retry0:
return (EINVAL);
}
+ nrrequeue = (int)(unsigned long)args->timeout;
+ nrwake = args->val;
+ /*
+ * Sanity check to prevent signed integer overflow,
+ * see Linux CVE-2018-6927
+ */
+ if (nrwake < 0 || nrrequeue < 0)
+ return (EINVAL);
+
retry1:
error = futex_get(args->uaddr, NULL, &f, flags | FUTEX_DONTLOCK);
if (error) {
@@ -938,8 +948,7 @@ retry1:
return (EAGAIN);
}
- nrwake = (int)(unsigned long)args->timeout;
- td->td_retval[0] = futex_requeue(f, args->val, f2, nrwake);
+ td->td_retval[0] = futex_requeue(f, nrwake, f2, nrrequeue);
futex_put(f2, NULL);
futex_put(f, NULL);
break;