unix: correctly track in-flight fds in sending process user_struct
authorHannes Frederic Sowa <hannes@stressinduktion.org>
Wed, 3 Feb 2016 01:11:03 +0000 (02:11 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 3 Mar 2016 23:06:20 +0000 (15:06 -0800)
commit341f09c01a7f26a030f3bedb08e4ce91e3ca24d3
treeae6b04fcf9a4ecf2c2196297be7f2c9711018ae7
parent59ae7b1c13bd615b09bff9d03aaa335559af604a
unix: correctly track in-flight fds in sending process user_struct

commit 415e3d3e90ce9e18727e8843ae343eda5a58fad6 upstream.

The commit referenced in the Fixes tag incorrectly accounted the number
of in-flight fds over a unix domain socket to the original opener
of the file-descriptor. This allows another process to arbitrary
deplete the original file-openers resource limit for the maximum of
open files. Instead the sending processes and its struct cred should
be credited.

To do so, we add a reference counted struct user_struct pointer to the
scm_fp_list and use it to account for the number of inflight unix fds.

Fixes: 712f4aad406bb1 ("unix: properly account for FDs passed over unix sockets")
Reported-by: David Herrmann <dh.herrmann@gmail.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
include/net/af_unix.h
include/net/scm.h
net/core/scm.c
net/unix/af_unix.c
net/unix/garbage.c