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linux(4): Prevent integer overflow in futex_requeue.

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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
This commit is contained in:
Dmitry Chagin 2021-06-10 14:23:11 +03:00
parent ee64d98204
commit 25b09d6f39
1 changed files with 15 additions and 6 deletions
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21
sys/compat/linux/linux_futex.c
View file

@ -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;