From 4e60f06d3bfcbcf84c6ded657dd435c83f11e3ff Mon Sep 17 00:00:00 2001
From: Yuxuan Shui <yshuiv7@gmail.com>
Date: Wed, 27 May 2020 04:08:02 +0100
Subject: [PATCH] ovl: initialize error in ovl_copy_xattr
Git-commit: 520da69d265a91c6536c63851cbb8a53946974f0
Patch-mainline: v5.8-rc1
References: bsc#1184176

In ovl_copy_xattr, if all the xattrs to be copied are overlayfs private
xattrs, the copy loop will terminate without assigning anything to the
error variable, thus returning an uninitialized value.

If ovl_copy_xattr is called from ovl_clear_empty, this uninitialized error
value is put into a pointer by ERR_PTR(), causing potential invalid memory
accesses down the line.

This commit initialize error with 0. This is the correct value because when
there's no xattr to copy, because all xattrs are private, ovl_copy_xattr
should succeed.

This bug is discovered with the help of INIT_STACK_ALL and clang.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
Link: https://bugs.chromium.org/p/chromium/issues/detail?id=1050405
Fixes: 0956254a2d5b ("ovl: don't copy up opaqueness")
Cc: stable@vger.kernel.org # v4.8
Signed-off-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: David Disseldorp <ddiss@suse.de>

---
 fs/overlayfs/copy_up.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index b801c6353100..ec5eca5a96f4 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -40,7 +40,7 @@ int ovl_copy_xattr(struct dentry *old, struct dentry *new)
 {
 	ssize_t list_size, size, value_size = 0;
 	char *buf, *name, *value = NULL;
-	int uninitialized_var(error);
+	int error = 0;
 	size_t slen;
 
 	if (!(old->d_inode->i_opflags & IOP_XATTR) ||
-- 
2.26.2