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ipc: Fail build if IPC structures change layout

PATCH In review Kees Cook 2 participants 2 messages May 19, 2017 – May 22, 2017

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Kees Cook

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PATCH 1/1 ipc: Fail build if IPC structures change layout

Since struct layout can be seen at build-time, turn runtime report into a build failure so it can be fixed more quickly.

Cc Manfred Spraul <[email protected]>
Signed-off-by Kees Cook <[email protected]>

---
Should be applied on top of the -mm tree's IPC changes

---
 ipc/msg.c | 5 +----
 ipc/sem.c | 5 +----
 ipc/shm.c | 5 +----
 3 files changed, 3 insertions(+), 12 deletions(-)
ipc/msg.c +1 -4
index e9785c4d2e0d..0ed7dae7d4e8 100644
@@ -118,10 +118,7 @@ static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 	key_t key = params->key;
 	int msgflg = params->flg;
 
-	if (offsetof(struct msg_queue, q_perm) != 0) {
-		pr_err("Invalid struct sem_perm, failing msgget().\n");
-		return -ENOMEM;
-	}
+	BUILD_BUG_ON(offsetof(struct msg_queue, q_perm) != 0);
 
 	msq = container_of(ipc_rcu_alloc(sizeof(*msq)), struct msg_queue,
 				q_perm);
ipc/sem.c +1 -4
index 18241c16d07c..2109fad750b5 100644
@@ -469,10 +469,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
 	if (ns->used_sems + nsems > ns->sc_semmns)
 		return -ENOSPC;
 
-	if (offsetof(struct sem_array, sem_perm) != 0) {
-		pr_err("Invalid struct sem_perm, failing semget().\n");
-		return -ENOMEM;
-	}
+	BUILD_BUG_ON(offsetof(struct sem_array, sem_perm) != 0);
 
 	size = sizeof(*sma) + nsems * sizeof(sma->sems[0]);
 	sma = container_of(ipc_rcu_alloc(size), struct sem_array, sem_perm);
ipc/shm.c +1 -4
index cec6df186050..2eb85bd5b855 100644
@@ -543,10 +543,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
 			ns->shm_tot + numpages > ns->shm_ctlall)
 		return -ENOSPC;
 
-	if (offsetof(struct shmid_kernel, shm_perm) != 0) {
-		pr_err("Invalid struct sem_perm, failing msgget().\n");
-		return -ENOMEM;
-	}
+	BUILD_BUG_ON(offsetof(struct shmid_kernel, shm_perm) != 0);
 
 	shp = container_of(ipc_rcu_alloc(sizeof(*shp)), struct shmid_kernel,
 				shm_perm);
Signature · 6 lines
2.7.4


-- 
Kees Cook
Pixel Security
#1 lore raw
Quoted 2 lines · On Fri, 19 May 2017 16:44:00 -0700 Kees Cook <[email protected]> wrote:

Since struct layout can be seen at build-time, turn runtime report into a build failure so it can be fixed more quickly.

I've just dropped the patch which this fixes, due to runtime issues. Manfred, please include this in the resend?