From: Ben Pfaff <blp@nicira.com>
Date: Wed, 9 Jul 2014 17:31:22 +0000 (-0700)
Subject: netlink: Fix handling of error from netlink_dump().
X-Git-Tag: cleanup-for-v3.18~248^2~21
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ac30ef832e6af0505b6f0251a6659adcfa74975e;p=pandora-kernel.git

netlink: Fix handling of error from netlink_dump().

netlink_dump() returns a negative errno value on error.  Until now,
netlink_recvmsg() directly recorded that negative value in sk->sk_err, but
that's wrong since sk_err takes positive errno values.  (This manifests as
userspace receiving a positive return value from the recv() system call,
falsely indicating success.) This bug was introduced in the commit that
started checking the netlink_dump() return value, commit b44d211 (netlink:
handle errors from netlink_dump()).

Multithreaded Netlink dumps are one way to trigger this behavior in
practice, as described in the commit message for the userspace workaround
posted here:
    http://openvswitch.org/pipermail/dev/2014-June/042339.html

This commit also fixes the same bug in netlink_poll(), introduced in commit
cd1df525d (netlink: add flow control for memory mapped I/O).

Signed-off-by: Ben Pfaff <blp@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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