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Thomas Graf authored
[ Upstream commit a18e6a18 ] 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@gmail.com> Signed-off-by: Thomas Graf <tgraf@suug.ch> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
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