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linux-next/net/l2tp
Tom Parkin 45faeff11b l2tp: make magic feather checks more useful
The l2tp tunnel and session structures contain a "magic feather" field
which was originally intended to help trace lifetime bugs in the code.

Since the introduction of the shared kernel refcount code in refcount.h,
and l2tp's porting to those APIs, we are covered by the refcount code's
checks and warnings.  Duplicating those checks in the l2tp code isn't
useful.

However, magic feather checks are still useful to help to detect bugs
stemming from misuse/trampling of the sk_user_data pointer in struct
sock.  The l2tp code makes extensive use of sk_user_data to stash
pointers to the tunnel and session structures, and if another subsystem
overwrites sk_user_data it's important to detect this.

As such, rework l2tp's magic feather checks to focus on validating the
tunnel and session data structures when they're extracted from
sk_user_data.

 * Add a new accessor function l2tp_sk_to_tunnel which contains a magic
   feather check, and is used by l2tp_core and l2tp_ip[6]
 * Comment l2tp_udp_encap_recv which doesn't use this new accessor function
   because of the specific nature of the codepath it is called in
 * Drop l2tp_session_queue_purge's check on the session magic feather:
   it is called from code which is walking the tunnel session list, and
   hence doesn't need validation
 * Drop l2tp_session_free's check on the tunnel magic feather: the
   intention of this check is covered by refcount.h's reference count
   sanity checking
 * Add session magic validation in pppol2tp_ioctl.  On failure return
   -EBADF, which mirrors the approach in pppol2tp_[sg]etsockopt.

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-09-03 12:19:03 -07:00
..
Kconfig treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
l2tp_core.c l2tp: make magic feather checks more useful 2020-09-03 12:19:03 -07:00
l2tp_core.h l2tp: make magic feather checks more useful 2020-09-03 12:19:03 -07:00
l2tp_debugfs.c l2tp: remove tunnel and session debug flags field 2020-08-22 12:44:37 -07:00
l2tp_eth.c l2tp: remove header length param from l2tp_xmit_skb 2020-09-03 12:19:03 -07:00
l2tp_ip6.c l2tp: make magic feather checks more useful 2020-09-03 12:19:03 -07:00
l2tp_ip.c l2tp: make magic feather checks more useful 2020-09-03 12:19:03 -07:00
l2tp_netlink.c l2tp: drop net argument from l2tp_tunnel_create 2020-09-03 12:19:03 -07:00
l2tp_ppp.c l2tp: make magic feather checks more useful 2020-09-03 12:19:03 -07:00
Makefile l2tp: add tracepoint infrastructure to core 2020-08-22 12:44:37 -07:00
trace.h l2tp: add tracepoint definitions in trace.h 2020-08-22 12:44:37 -07:00