linux-kernel - [PATCH] ipc/shm: Use ERR_CAST() for shm

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Date:   Wed, 19 Sep 2018 11:07:22 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Davidlohr Bueso <dbueso@...e.de>,
        Manfred Spraul <manfred@...orfullife.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] ipc/shm: Use ERR_CAST() for shm_lock() error return

This uses ERR_CAST() instead of an open-coded cast, as it is casting
across structure pointers, which upsets __randomize_layout:

ipc/shm.c: In function ‘shm_lock’:
ipc/shm.c:209:9: note: randstruct: casting between randomized structure pointer types (ssa): ‘struct shmid_kernel’ and ‘struct kern_ipc_perm’

  return (void *)ipcp;
         ^~~~~~~~~~~~

Fixes: 82061c57ce93 ("ipc: drop ipc_lock()")
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 ipc/shm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index 4cd402e4cfeb..1c65fb357395 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -206,7 +206,7 @@ static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)
 	 * Callers of shm_lock() must validate the status of the returned ipc
 	 * object pointer and error out as appropriate.
 	 */
-	return (void *)ipcp;
+	return ERR_CAST(ipcp);
 }
 
 static inline void shm_lock_by_ptr(struct shmid_kernel *ipcp)
-- 
2.17.1


-- 
Kees Cook
Pixel Security