1 files changed, 19 insertions, 3 deletions

diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index da8876d38a7b..9c098db43344 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -91,7 +91,24 @@ static int autofs4_write(struct autofs_sb_info *sbi,
 
         return (bytes > 0);
 }
-        
+
+/*
+ * The autofs_v5 packet was misdesigned.
+ *
+ * The packets are identical on x86-32 and x86-64, but have different
+ * alignment. Which means that 'sizeof()' will give different results.
+ * Fix it up for the case of running 32-bit user mode on a 64-bit kernel.
+ */
+static noinline size_t autofs_v5_packet_size(struct autofs_sb_info *sbi)
+{
+        size_t pktsz = sizeof(struct autofs_v5_packet);
+#if defined(CONFIG_X86_64) && defined(CONFIG_COMPAT)
+        if (sbi->compat_daemon > 0)
+                pktsz -= 4;
+#endif
+        return pktsz;
+}
+
 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
                                  struct autofs_wait_queue *wq,
                                  int type)
@@ -155,8 +172,7 @@ static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
         {
                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 
-                pktsz = sizeof(*packet);
-
+                pktsz = autofs_v5_packet_size(sbi);
                 packet->wait_queue_token = wq->wait_queue_token;
                 packet->len = wq->name.len;
                 memcpy(packet->name, wq->name.name, wq->name.len);