fs/binfmt_elf.c: allocate initialized memory in fill_thread_core_info()

mainline inclusion
from mainline-next
commit bb77be1c3196eb3c05ec68f4ffeb155503053d09
category: bugfix
bugzilla: 13690
CVE: CVE-2020-10732

-------------------------------------------------

KMSAN reported uninitialized data being written to disk when dumping core.
As a result, several kilobytes of kmalloc memory may be written to the
core file and then read by a non-privileged user.

Link: http://lkml.kernel.org/r/20200419100848.63472-1-glider@google.com
Link: https://github.com/google/kmsan/issues/76Signed-off-by: NAlexander Potapenko <glider@google.com>
Reported-by: Nsam <sunhaoyl@outlook.com>
Acked-by: NKees Cook <keescook@chromium.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/binfmt_elf.c

@@ -1766,7 +1766,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 		    (!regset->active || regset->active(t->task, regset) > 0)) {
 			int ret;
 			size_t size = regset_size(t->task, regset);
-			void *data = kmalloc(size, GFP_KERNEL);
+			void *data = kzalloc(size, GFP_KERNEL);
 			if (unlikely(!data))
 				return 0;
 			ret = regset->get(t->task, regset,