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authorKees Cook <keescook@chromium.org>2018-08-25 22:58:01 -0700
committerDavid S. Miller <davem@davemloft.net>2018-08-26 14:21:50 -0700
commit98c8f125fd8a6240ea343c1aa50a1be9047791b8 (patch)
tree89585edf9ee579356c6ec71c73ef223acbab0eba
parente75d039a54090470b7a42e803fd4f9398390f907 (diff)
download96b-common-98c8f125fd8a6240ea343c1aa50a1be9047791b8.tar.gz
net: sched: Fix memory exposure from short TCA_U32_SEL
Via u32_change(), TCA_U32_SEL has an unspecified type in the netlink policy, so max length isn't enforced, only minimum. This means nkeys (from userspace) was being trusted without checking the actual size of nla_len(), which could lead to a memory over-read, and ultimately an exposure via a call to u32_dump(). Reachability is CAP_NET_ADMIN within a namespace. Reported-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Jiri Pirko <jiri@resnulli.us> Cc: "David S. Miller" <davem@davemloft.net> Cc: netdev@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/sched/cls_u32.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index d5d2a6dc3921..f218ccf1e2d9 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -914,6 +914,7 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
struct nlattr *opt = tca[TCA_OPTIONS];
struct nlattr *tb[TCA_U32_MAX + 1];
u32 htid, flags = 0;
+ size_t sel_size;
int err;
#ifdef CONFIG_CLS_U32_PERF
size_t size;
@@ -1076,8 +1077,13 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
}
s = nla_data(tb[TCA_U32_SEL]);
+ sel_size = struct_size(s, keys, s->nkeys);
+ if (nla_len(tb[TCA_U32_SEL]) < sel_size) {
+ err = -EINVAL;
+ goto erridr;
+ }
- n = kzalloc(sizeof(*n) + s->nkeys*sizeof(struct tc_u32_key), GFP_KERNEL);
+ n = kzalloc(offsetof(typeof(*n), sel) + sel_size, GFP_KERNEL);
if (n == NULL) {
err = -ENOBUFS;
goto erridr;
@@ -1092,7 +1098,7 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
}
#endif
- memcpy(&n->sel, s, sizeof(*s) + s->nkeys*sizeof(struct tc_u32_key));
+ memcpy(&n->sel, s, sel_size);
RCU_INIT_POINTER(n->ht_up, ht);
n->handle = handle;
n->fshift = s->hmask ? ffs(ntohl(s->hmask)) - 1 : 0;