[PATCH (urgent)] vfs: fix uninitialized uid/gid in chown_common()

[Tetsuo Handa]

syzbot is reporting uninit-value in tomoyo_path_chown() [1], for
chown_common() is by error passing uninitialized newattrs.ia_vfsuid to
security_path_chown() via from_vfsuid() when user == -1 is passed.
We must initialize newattrs.ia_vfs{u,g}id fields in order to make
from_vfs{u,g}id() work.

Link: https://syzkaller.appspot.com/bug?extid=541e21dcc32c4046cba9 [1]
Reported-by: syzbot <syzbot+541e21dcc32c4046cba9 at syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
---
 fs/open.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/open.c b/fs/open.c
index 8a813fa5ca56..0550efb7b53a 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -709,6 +709,8 @@ int chown_common(const struct path *path, uid_t user, gid_t group)
 	kuid_t uid;
 	kgid_t gid;
 
+	newattrs.ia_vfsuid = VFSUIDT_INIT(KUIDT_INIT(-1));
+	newattrs.ia_vfsgid = VFSGIDT_INIT(KGIDT_INIT(-1));
 	uid = make_kuid(current_user_ns(), user);
 	gid = make_kgid(current_user_ns(), group);
 
-- 
2.34.1