linux-user: Conditionally Pass Attribute Pointer to mq_open()

The mq_open system call takes an optional struct mq_attr pointer
argument in the fourth position.  This pointer is used when O_CREAT
is specified in the flags (second) argument.  It may be NULL, in
which case the queue is created with implementation defined attributes.

Change the code to properly handle the case when NULL is passed in the
arg4 position.

Signed-off-by: Tom Musta <tommusta@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index fa8ba8fe7c..e754dbb3fa 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -9115,12 +9115,16 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
 #if defined(TARGET_NR_mq_open) && defined(__NR_mq_open)
     case TARGET_NR_mq_open:
         {
-            struct mq_attr posix_mq_attr;
+            struct mq_attr posix_mq_attr, *attrp;
 
             p = lock_user_string(arg1 - 1);
-            if (arg4 != 0)
+            if (arg4 != 0) {
                 copy_from_user_mq_attr (&posix_mq_attr, arg4);
-            ret = get_errno(mq_open(p, arg2, arg3, &posix_mq_attr));
+                attrp = &posix_mq_attr;
+            } else {
+                attrp = 0;
+            }
+            ret = get_errno(mq_open(p, arg2, arg3, attrp));
             unlock_user (p, arg1, 0);
         }
         break;