[PATCH 3.16 61/61] fs/binfmt_elf.c: allocate initialized memory in fill_thread_core_info()

[Ben Hutchings]

3.16.85-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Alexander Potapenko <glider@xxxxxxxxxx>

commit 1d605416fb7175e1adf094251466caa52093b413 upstream.

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 <sunhaoyl@xxxxxxxxxxx>
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Link: http://lkml.kernel.org/r/20200419100848.63472-1-glider@xxxxxxxxxx
Link: https://github.com/google/kmsan/issues/76
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/binfmt_elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1575,7 +1575,7 @@ static int fill_thread_core_info(struct
 		    (!regset->active || regset->active(t->task, regset) > 0)) {
 			int ret;
 			size_t size = regset->n * regset->size;
-			void *data = kmalloc(size, GFP_KERNEL);
+			void *data = kzalloc(size, GFP_KERNEL);
 			if (unlikely(!data))
 				return 0;
 			ret = regset->get(t->task, regset,