From ade9f91b32b964e83d294f4973d50083b08ef6fc Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Wed, 2 Aug 2017 13:32:21 -0700
Subject: [PATCH] ipc: add missing container_of()s for randstruct
Git-commit: ade9f91b32b964e83d294f4973d50083b08ef6fc
Patch-mainline: v4.13-rc4
References: bsc#1050323

When building with the randstruct gcc plugin, the layout of the IPC
structs will be randomized, which requires any sub-structure accesses to
use container_of().  The proc display handlers were missing the needed
container_of()s since the iterator is passing in the top-level struct
kern_ipc_perm.

This would lead to crashes when running the "lsipc" program after the
system had IPC registered (e.g. after starting up Gnome):

  general protection fault: 0000 [#1] PREEMPT SMP
  ...
  RIP: 0010:shm_add_rss_swap.isra.1+0x13/0xa0
  ...
  Call Trace:
    sysvipc_shm_proc_show+0x5e/0x150
    sysvipc_proc_show+0x1a/0x30
    seq_read+0x2e9/0x3f0
  ...

Link: http://lkml.kernel.org/r/20170730205950.GA55841@beast
Fixes: 3859a271a003 ("randstruct: Mark various structs for randomization")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>

---
 ipc/msg.c | 3 ++-
 ipc/sem.c | 3 ++-
 ipc/shm.c | 4 +++-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/ipc/msg.c b/ipc/msg.c
index 5b25e0755656..2c38f10d1483 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -1034,7 +1034,8 @@ void msg_exit_ns(struct ipc_namespace *ns)
 static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
 {
 	struct user_namespace *user_ns = seq_user_ns(s);
-	struct msg_queue *msq = it;
+	struct kern_ipc_perm *ipcp = it;
+	struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 
 	seq_printf(s,
 		   "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
diff --git a/ipc/sem.c b/ipc/sem.c
index 9e70cd7a17da..38371e93bfa5 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -2179,7 +2179,8 @@ void exit_sem(struct task_struct *tsk)
 static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
 {
 	struct user_namespace *user_ns = seq_user_ns(s);
-	struct sem_array *sma = it;
+	struct kern_ipc_perm *ipcp = it;
+	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
 	time_t sem_otime;
 
 	/*
diff --git a/ipc/shm.c b/ipc/shm.c
index 28a444861a8f..8828b4c3a190 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -1380,9 +1380,11 @@ SYSCALL_DEFINE1(shmdt, char __user *, shmaddr)
 static int sysvipc_shm_proc_show(struct seq_file *s, void *it)
 {
 	struct user_namespace *user_ns = seq_user_ns(s);
-	struct shmid_kernel *shp = it;
+	struct kern_ipc_perm *ipcp = it;
+	struct shmid_kernel *shp;
 	unsigned long rss = 0, swp = 0;
 
+	shp = container_of(ipcp, struct shmid_kernel, shm_perm);
 	shm_add_rss_swap(shp, &rss, &swp);
 
 #if BITS_PER_LONG <= 32
-- 
2.12.0