[PATCH v2 1/3] mm/gup_benchmark: handle gup failures

["Michael S. Tsirkin" <mst@redhat.com>]

__gup_benchmark_ioctl does not handle the case where
get_user_pages_fast fails:

- a negative return code will cause a buffer overrun
- returning with partial success will cause use of
  uninitialized memory.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thorsten Leemhuis <regressions@leemhuis.info>
Cc: stable@vger.kernel.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 mm/gup_benchmark.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
index 5c8e2ab..d743035 100644
--- a/mm/gup_benchmark.c
+++ b/mm/gup_benchmark.c
@@ -23,7 +23,7 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
 	struct page **pages;
 
 	nr_pages = gup->size / PAGE_SIZE;
-	pages = kvmalloc(sizeof(void *) * nr_pages, GFP_KERNEL);
+	pages = kvzalloc(sizeof(void *) * nr_pages, GFP_KERNEL);
 	if (!pages)
 		return -ENOMEM;
 
@@ -41,7 +41,8 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
 		}
 
 		nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i);
-		i += nr;
+		if (nr > 0)
+			i += nr;
 	}
 	end_time = ktime_get();
 
-- 
MST