ppp: ensure file->private_data can't be overridden
authorGuillaume Nault <g.nault@alphalink.fr>
Mon, 14 Mar 2016 20:17:16 +0000 (21:17 +0100)
committerBen Hutchings <ben@decadent.org.uk>
Sat, 30 Apr 2016 22:05:18 +0000 (00:05 +0200)
commit e8e56ffd9d2973398b60ece1f1bebb8d67b4d032 upstream.

Locking ppp_mutex must be done before dereferencing file->private_data,
otherwise it could be modified before ppp_unattached_ioctl() takes the
lock. This could lead ppp_unattached_ioctl() to override ->private_data,
thus leaking reference to the ppp_file previously pointed to.

v2: lock all ppp_ioctl() instead of just checking private_data in
    ppp_unattached_ioctl(), to avoid ambiguous behaviour.

Fixes: f3ff8a4d80e8 ("ppp: push BKL down into the driver")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
drivers/net/ppp/ppp_generic.c

Simple merge