mount.cifs: check access of credential files before opening
It's possible for an unprivileged user to pass a setuid mount.cifs a
credential or password file to which he does not have access. This can cause
mount.cifs to open the file on his behalf and possibly leak the info in the
first few lines of the file.
Check the access permissions of the file before opening it.
Reported-by: Ronald Volgers <r.c.volgers@student.utwente.nl>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Steve French <sfrench@us.ibm.com>
Part 1/2 of a fix for CVE-2009-2948.
(cherry picked from commit
b656deb5d7e97176c32b61b7659258846db16887)