[Qemu-devel] [PATCH 02/12] linux-user: Dereference Pointer Argument to ipc/semctl Sys Call

[Tom Musta <tommusta@gmail.com>]

When the ipc system call is used to wrap a semctl system call,
the ptr argument to ipc needs to be dereferenced prior to passing
it to the semctl handler.  This is because the fourth argument to
semctl is a union and not a pointer to a union.

Signed-off-by: Tom Musta <tommusta@gmail.com>

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 540001c..229c482 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -3135,9 +3135,15 @@ static abi_long do_ipc(unsigned int call, int first,
         ret = get_errno(semget(first, second, third));
         break;
 
-    case IPCOP_semctl:
-        ret = do_semctl(first, second, third, (union target_semun)(abi_ulong) ptr);
+    case IPCOP_semctl: {
+        /* The semun argument to semctl is passed by value, so dereference the
+         * ptr argument. */
+        abi_ulong atptr;
+        get_user_ual(atptr, (abi_ulong)ptr);
+        ret = do_semctl(first, second, third,
+                (union target_semun)(abi_ulong) atptr);
         break;
+    }
 
     case IPCOP_msgget:
         ret = get_errno(msgget(first, second));
-- 
1.7.1