[PATCH 6/6] sysvipc: Return EINVAL for invalid shmctl commands

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

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).
---
 sysdeps/unix/sysv/linux/shmctl.c | 41 ++++++++++++++++++++++++--------
 sysvipc/test-sysvshm.c           |  5 ++++
 2 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/shmctl.c b/sysdeps/unix/sysv/linux/shmctl.c
index 1d19a798b1..98eae91482 100644
--- a/sysdeps/unix/sysv/linux/shmctl.c
+++ b/sysdeps/unix/sysv/linux/shmctl.c
@@ -88,25 +88,46 @@ __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:
+      arg = NULL;
+      break;
+
+    case IPC_SET:
+    case IPC_STAT:
+    case SHM_STAT:
+#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->msg_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)
diff --git a/sysvipc/test-sysvshm.c b/sysvipc/test-sysvshm.c
index f083fd280b..a1b8b4823e 100644
--- a/sysvipc/test-sysvshm.c
+++ b/sysvipc/test-sysvshm.c
@@ -25,6 +25,8 @@
 #include <sys/ipc.h>
 #include <sys/shm.h>
 
+#include <test-sysvipc.h>
+
 #include <support/support.h>
 #include <support/check.h>
 #include <support/temp_file.h>
@@ -81,6 +83,9 @@ do_test (void)
       FAIL_EXIT1 ("shmget failed (errno=%d)", errno);
     }
 
+  TEST_COMPARE (shmctl (shmid, first_shm_invalid_cmd (), NULL), -1);
+  TEST_COMPARE (errno, EINVAL);
+
   /* Get shared memory kernel information and do some sanity checks.  */
   struct shmid_ds shminfo;
   if (shmctl (shmid, IPC_STAT, &shminfo) == -1)
-- 
2.25.1