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

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.

Reported-by: sam <[email protected]>
Signed-off-by: Alexander Potapenko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Kees Cook <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Link: google/kmsan#76
Signed-off-by: Linus Torvalds <[email protected]>

fs/binfmt_elf.c

@@ -1733,7 +1733,7 @@ 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,