sysvipc: Return EINVAL for invalid shmctl commands

It avoids regressions on possible future commands that might require
additional libc support.  The downside is new commands added by newer
kernels will need further glibc support.

Checked on x86_64-linux-gnu and i686-linux-gnu (Linux v4.15 and v5.4).

1 files changed, 34 insertions, 10 deletions

diff --git a/sysdeps/unix/sysv/linux/shmctl.c b/sysdeps/unix/sysv/linux/shmctl.c
index 1d19a798b1..833f013e69 100644
--- a/sysdeps/unix/sysv/linux/shmctl.c
+++ b/sysdeps/unix/sysv/linux/shmctl.c
@@ -88,25 +88,49 @@ __shmctl64 (int shmid, int cmd, struct __shmid64_ds *buf)
 {
 #if __IPC_TIME64
   struct kernel_shmid64_ds kshmid, *arg = NULL;
-  if (buf != NULL)
+#else
+  shmctl_arg_t *arg;
+#endif
+
+  switch (cmd)
     {
-      /* This is a Linux extension where kernel expects either a
-	 'struct shminfo' (IPC_INFO) or 'struct shm_info' (SHM_INFO).  */
-      if (cmd == IPC_INFO || cmd == SHM_INFO)
-	arg = (struct kernel_shmid64_ds *) buf;
-      else
+    case IPC_RMID:
+    case SHM_LOCK:
+    case SHM_UNLOCK:
+      arg = NULL;
+      break;
+
+    case IPC_SET:
+    case IPC_STAT:
+    case SHM_STAT:
+    case SHM_STAT_ANY:
+#if __IPC_TIME64
+      if (buf != NULL)
 	{
 	  shmid64_to_kshmid64 (buf, &kshmid);
 	  arg = &kshmid;
 	}
-    }
 # ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
-  if (cmd == IPC_SET)
-    arg->shm_perm.mode *= 0x10000U;
+      if (cmd == IPC_SET)
+        arg->shm_perm.mode *= 0x10000U;
 # endif
 #else
-  shmctl_arg_t *arg = buf;
+      arg = buf;
 #endif
+      break;
+
+    case IPC_INFO:
+    case SHM_INFO:
+      /* This is a Linux extension where kernel expects either a
+	 'struct shminfo' (IPC_INFO) or 'struct shm_info' (SHM_INFO).  */
+      arg = (__typeof__ (arg)) buf;
+      break;
+
+    default:
+      __set_errno (EINVAL);
+      return -1;
+    }
+
 
   int ret = shmctl_syscall (shmid, cmd, arg);
   if (ret < 0)