Merge tag 's390-6.0-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

Pull s390 fixes from Vasily Gorbik:

 - Fix double free of guarded storage and runtime instrumentation
   control blocks on fork() failure

 - Fix triggering write fault when VMA does not allow VM_WRITE

* tag 's390-6.0-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/mm: do not trigger write fault when vma does not allow VM_WRITE
  s390: fix double free of GS and RI CBs on fork() failure

2 files changed, 19 insertions, 7 deletions

diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 89949b9f3cf8..d5119e039d85 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -91,6 +91,18 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 
 	memcpy(dst, src, arch_task_struct_size);
 	dst->thread.fpu.regs = dst->thread.fpu.fprs;
+
+	/*
+	 * Don't transfer over the runtime instrumentation or the guarded
+	 * storage control block pointers. These fields are cleared here instead
+	 * of in copy_thread() to avoid premature freeing of associated memory
+	 * on fork() failure. Wait to clear the RI flag because ->stack still
+	 * refers to the source thread.
+	 */
+	dst->thread.ri_cb = NULL;
+	dst->thread.gs_cb = NULL;
+	dst->thread.gs_bc_cb = NULL;
+
 	return 0;
 }
 
@@ -150,13 +162,11 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	frame->childregs.flags = 0;
 	if (new_stackp)
 		frame->childregs.gprs[15] = new_stackp;
-
-	/* Don't copy runtime instrumentation info */
-	p->thread.ri_cb = NULL;
+	/*
+	 * Clear the runtime instrumentation flag after the above childregs
+	 * copy. The CB pointer was already cleared in arch_dup_task_struct().
+	 */
 	frame->childregs.psw.mask &= ~PSW_MASK_RI;
-	/* Don't copy guarded storage control block */
-	p->thread.gs_cb = NULL;
-	p->thread.gs_bc_cb = NULL;
 
 	/* Set a new TLS ?  */
 	if (clone_flags & CLONE_SETTLS) {
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 13449941516c..09b6e756d521 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -379,7 +379,9 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
 	flags = FAULT_FLAG_DEFAULT;
 	if (user_mode(regs))
 		flags |= FAULT_FLAG_USER;
-	if (access == VM_WRITE || is_write)
+	if (is_write)
+		access = VM_WRITE;
+	if (access == VM_WRITE)
 		flags |= FAULT_FLAG_WRITE;
 	mmap_read_lock(mm);