gru: check for valid vma

Fix bug caused by failure to allocate a GRU gts structure.  The old code
failed to handle the case where the vma was invalid.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 9 deletions

diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
index ada7df7e0968..7466234450f3 100644
--- a/drivers/misc/sgi-gru/grufault.c
+++ b/drivers/misc/sgi-gru/grufault.c
@@ -90,19 +90,22 @@ static struct gru_thread_state *gru_alloc_locked_gts(unsigned long vaddr)
 {
         struct mm_struct *mm = current->mm;
         struct vm_area_struct *vma;
-        struct gru_thread_state *gts = NULL;
+        struct gru_thread_state *gts = ERR_PTR(-EINVAL);
 
         down_write(&mm->mmap_sem);
         vma = gru_find_vma(vaddr);
-        if (vma)
-                gts = gru_alloc_thread_state(vma, TSID(vaddr, vma));
-        if (!IS_ERR(gts)) {
-                mutex_lock(&gts->ts_ctxlock);
-                downgrade_write(&mm->mmap_sem);
-        } else {
-                up_write(&mm->mmap_sem);
-        }
+        if (!vma)
+                goto err;
+
+        gts = gru_alloc_thread_state(vma, TSID(vaddr, vma));
+        if (IS_ERR(gts))
+                goto err;
+        mutex_lock(&gts->ts_ctxlock);
+        downgrade_write(&mm->mmap_sem);
+        return gts;
 
+err:
+        up_write(&mm->mmap_sem);
         return gts;
 }