The branch main has been updated by dchagin:
URL:
https://cgit.FreeBSD.org/src/commit/?id=25b09d6f398ea8a260ee8e2e8209fd76c61e13ee
commit 25b09d6f398ea8a260ee8e2e8209fd76c61e13ee
Author: Dmitry Chagin <dcha...@freebsd.org>
AuthorDate: 2021-06-10 11:23:11 +0000
Commit: Dmitry Chagin <dcha...@freebsd.org>
CommitDate: 2021-06-10 11:23:11 +0000
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.
MFC after: 2 weeks
---
sys/compat/linux/linux_futex.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/sys/compat/linux/linux_futex.c b/sys/compat/linux/linux_futex.c
index da1a91916869..11836e93d71c 100644
--- a/sys/compat/linux/linux_futex.c
+++ b/sys/compat/linux/linux_futex.c
@@ -520,7 +520,8 @@ 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;
@@ -529,7 +530,7 @@ futex_requeue(struct futex *f, int n, struct futex *f2, int
n2)
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;
@@ -555,7 +556,7 @@ 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;
}
}
@@ -657,7 +658,7 @@ 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;
@@ -786,6 +787,15 @@ 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)
@@ -829,8 +839,7 @@ 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;
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