genetlink: fix family dump race
authorJohannes Berg <johannes.berg@intel.com>
Tue, 13 Aug 2013 07:04:05 +0000 (09:04 +0200)
committerDavid S. Miller <davem@davemloft.net>
Tue, 13 Aug 2013 07:57:06 +0000 (00:57 -0700)
commit58ad436fcf49810aa006016107f494c9ac9013db
tree0853904283d081562e2c07bed067c36e03936c0c
parent771085d6bf3c52de29fc213e5bad07a82e57c23e
genetlink: fix family dump race

When dumping generic netlink families, only the first dump call
is locked with genl_lock(), which protects the list of families,
and thus subsequent calls can access the data without locking,
racing against family addition/removal. This can cause a crash.
Fix it - the locking needs to be conditional because the first
time around it's already locked.

A similar bug was reported to me on an old kernel (3.4.47) but
the exact scenario that happened there is no longer possible,
on those kernels the first round wasn't locked either. Looking
at the current code I found the race described above, which had
also existed on the old kernel.

Cc: stable@vger.kernel.org
Reported-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/netlink/genetlink.c