From: "Michael S. Tsirkin" mst@redhat.com Subject: mm/gup_benchmark: handle gup failures
Patch series "mm/get_user_pages_fast fixes, cleanups", v2.
Turns out get_user_pages_fast and __get_user_pages_fast return different values on error when given a single page: __get_user_pages_fast returns 0. get_user_pages_fast returns either 0 or an error.
Callers of get_user_pages_fast expect an error so fix it up to return an error consistently.
Stress the difference between get_user_pages_fast and __get_user_pages_fast to make sure callers aren't confused.
This patch (of 3):
__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.
[akpm@linux-foundation.org: simplification] Link: http://lkml.kernel.org/r/1522962072-182137-3-git-send-email-mst@redhat.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com 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: Andrew Morton akpm@linux-foundation.org ---
mm/gup_benchmark.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff -puN mm/gup_benchmark.c~mm-gup_benchmark-handle-gup-failures mm/gup_benchmark.c --- a/mm/gup_benchmark.c~mm-gup_benchmark-handle-gup-failures +++ a/mm/gup_benchmark.c @@ -23,7 +23,7 @@ static int __gup_benchmark_ioctl(unsigne 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;
@@ -41,6 +41,8 @@ static int __gup_benchmark_ioctl(unsigne }
nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i); + if (nr <= 0) + break; i += nr; } end_time = ktime_get(); _