[v2.6.34-stable 123/165] netlink: validate NLA_MSECS length

[Paul Gortmaker]

From: Johannes Berg <johannes.berg@xxxxxxxxx>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit c30bc94758ae2a38a5eb31767c1985c0aae0950b upstream.

L2TP for example uses NLA_MSECS like this:
policy:
        [L2TP_ATTR_RECV_TIMEOUT]        = { .type = NLA_MSECS, },
code:
        if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
                cfg.reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);

As nla_get_msecs() is essentially nla_get_u64() plus the
conversion to a HZ-based value, this will not properly
reject attributes from userspace that aren't long enough
and might overrun the message.

Add NLA_MSECS to the attribute minlen array to check the
size properly.

Cc: Thomas Graf <tgraf@xxxxxxx>
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 lib/nlattr.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/nlattr.c b/lib/nlattr.c
index c4706eb..109d4fe 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -20,6 +20,7 @@ static u16 nla_attr_minlen[NLA_TYPE_MAX+1] __read_mostly = {
 	[NLA_U16]	= sizeof(u16),
 	[NLA_U32]	= sizeof(u32),
 	[NLA_U64]	= sizeof(u64),
+	[NLA_MSECS]	= sizeof(u64),
 	[NLA_NESTED]	= NLA_HDRLEN,
 };
 
-- 
1.7.12.rc2

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