4.13-stable review patch. If anyone has any objections, please let me know.
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From: Johannes Berg johannes.berg@intel.com
[ Upstream commit 48044eb490be71c203e14dd89e8bae87209eab52 ]
It seems that it's possible to toggle NETLINK_F_EXT_ACK through setsockopt() while another thread/CPU is building a message inside netlink_ack(), which could then trigger the WARN_ON()s I added since if it goes from being turned off to being turned on between allocating and filling the message, the skb could end up being too small.
Avoid this whole situation by storing the value of this flag in a separate variable and using that throughout the function instead.
Fixes: 2d4bc93368f5 ("netlink: extended ACK reporting") Signed-off-by: Johannes Berg johannes.berg@intel.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/netlink/af_netlink.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
--- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2299,6 +2299,7 @@ void netlink_ack(struct sk_buff *in_skb, size_t tlvlen = 0; struct netlink_sock *nlk = nlk_sk(NETLINK_CB(in_skb).sk); unsigned int flags = 0; + bool nlk_has_extack = nlk->flags & NETLINK_F_EXT_ACK;
/* Error messages get the original request appened, unless the user * requests to cap the error message, and get extra error data if @@ -2309,7 +2310,7 @@ void netlink_ack(struct sk_buff *in_skb, payload += nlmsg_len(nlh); else flags |= NLM_F_CAPPED; - if (nlk->flags & NETLINK_F_EXT_ACK && extack) { + if (nlk_has_extack && extack) { if (extack->_msg) tlvlen += nla_total_size(strlen(extack->_msg) + 1); if (extack->bad_attr) @@ -2318,8 +2319,7 @@ void netlink_ack(struct sk_buff *in_skb, } else { flags |= NLM_F_CAPPED;
- if (nlk->flags & NETLINK_F_EXT_ACK && - extack && extack->cookie_len) + if (nlk_has_extack && extack && extack->cookie_len) tlvlen += nla_total_size(extack->cookie_len); }
@@ -2347,7 +2347,7 @@ void netlink_ack(struct sk_buff *in_skb, errmsg->error = err; memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh));
- if (nlk->flags & NETLINK_F_EXT_ACK && extack) { + if (nlk_has_extack && extack) { if (err) { if (extack->_msg) WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG,