3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Graf <tgraf@xxxxxxx> [ Upstream commit a18e6a186f53af06937a2c268c72443336f4ab56 ] Each mmap Netlink frame contains a status field which indicates whether the frame is unused, reserved, contains data or needs to be skipped. Both loads and stores may not be reordeded and must complete before the status field is changed and another CPU might pick up the frame for use. Use an smp_mb() to cover needs of both types of callers to netlink_set_status(), callers which have been reading data frame from the frame, and callers which have been filling or releasing and thus writing to the frame. - Example code path requiring a smp_rmb(): memcpy(skb->data, (void *)hdr + NL_MMAP_HDRLEN, hdr->nm_len); netlink_set_status(hdr, NL_MMAP_STATUS_UNUSED); - Example code path requiring a smp_wmb(): hdr->nm_uid = from_kuid(sk_user_ns(sk), NETLINK_CB(skb).creds.uid); hdr->nm_gid = from_kgid(sk_user_ns(sk), NETLINK_CB(skb).creds.gid); netlink_frame_flush_dcache(hdr); netlink_set_status(hdr, NL_MMAP_STATUS_VALID); Fixes: f9c228 ("netlink: implement memory mapped recvmsg()") Reported-by: Eric Dumazet <eric.dumazet@xxxxxxxxx> Signed-off-by: Thomas Graf <tgraf@xxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/netlink/af_netlink.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -535,9 +535,9 @@ static enum nl_mmap_status netlink_get_s static void netlink_set_status(struct nl_mmap_hdr *hdr, enum nl_mmap_status status) { + smp_mb(); hdr->nm_status = status; flush_dcache_page(pgvec_to_page(hdr)); - smp_wmb(); } static struct nl_mmap_hdr * -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html