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

[Michael S. Tsirkin]

__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.shute...@linux.intel.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Huang Ying <ying.hu...@intel.com>
Cc: Jonathan Corbet <cor...@lwn.net>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Thorsten Leemhuis <regressi...@leemhuis.info>
Cc: sta...@vger.kernel.org
Signed-off-by: Michael S. Tsirkin <m...@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