parasite: unprotect VMA-s if one of DUMPPAGES operations failed

PARASITE_CMD_DUMPPAGES is called many times and the parasite args
contains an array with vmas at this time, so VMAs can be unprotected in
error case
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

pie/parasite.c

@@ -22,6 +22,12 @@ static int tsock = -1;
 
 static struct rt_sigframe *sigframe;
 
+/*
+ * PARASITE_CMD_DUMPPAGES is called many times and the parasite args contains
+ * an array of VMAs at this time, so VMAs can be unprotected in any moment
+ */
+static struct parasite_dump_pages_args *mprotect_args = NULL;
+
 #ifndef SPLICE_F_GIFT
 #define SPLICE_F_GIFT	0x08
 #endif
@@ -42,6 +48,11 @@ static int mprotect_vmas(struct parasite_dump_pages_args *args)
 		}
 	}
 
+	if (args->add_prot)
+		mprotect_args = args;
+	else
+		mprotect_args = NULL;
+
 	return ret;
 }
 
@@ -435,6 +446,11 @@ static int fini()
 {
 	unsigned long new_sp;
 
+	if (mprotect_args) {
+		mprotect_args->add_prot = 0;
+		mprotect_vmas(mprotect_args);
+	}
+
 	new_sp = (long)sigframe + SIGFRAME_OFFSET;
 	pr_debug("%ld: new_sp=%lx ip %lx\n", sys_gettid(),
 		  new_sp, RT_SIGFRAME_REGIP(sigframe));