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authorThomas Graf <tgraf@suug.ch>2014-12-18 10:30:26 +0000
committerDavid S. Miller <davem@davemloft.net>2014-12-18 12:35:55 -0500
commita18e6a186f53af06937a2c268c72443336f4ab56 (patch)
tree8a230f02609ca813834668a1582807bafcd6ae2b
parent4682a0358639b29cf69437ed909c6221f8c89847 (diff)
downloadop-kernel-dev-a18e6a186f53af06937a2c268c72443336f4ab56.zip
op-kernel-dev-a18e6a186f53af06937a2c268c72443336f4ab56.tar.gz
netlink: Don't reorder loads/stores before marking mmap netlink frame as available
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>
-rw-r--r--net/netlink/af_netlink.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index a64680a..074cf3e 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -550,9 +550,9 @@ static enum nl_mmap_status netlink_get_status(const struct nl_mmap_hdr *hdr)
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 *
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