4.18-stable review patch. If anyone has any objections, please let me know.
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From: Kees Cook keescook@chromium.org
[ Upstream commit 98c8f125fd8a6240ea343c1aa50a1be9047791b8 ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/cls_u32.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
--- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c @@ -912,6 +912,7 @@ static int u32_change(struct net *net, s 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; @@ -1074,8 +1075,13 @@ static int u32_change(struct net *net, s }
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; @@ -1090,7 +1096,7 @@ static int u32_change(struct net *net, s } #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;