An updated cifs-utils package that fixes a bug is now available for Red Hat Enterprise Linux 6.
The Server Message Block (SMB), also known as Common Internet File System (CIFS), is a standard file-sharing protocol widely deployed on Windows machines. The tools included in this package work in conjunction with support in the kernel to allow users to mount a SMB/CIFS share onto a client, and use it as if it were a standard Linux file system.
Due to an error in the cifs.upcall utility, Generic Security Services Application Program Interface (GSSAPI) channel bindings in Kerberos authentication messages were not set properly. This would cause some servers to reject authentication requests. Consequent to this, an attempt to mount a CIFS share with the security mode set to "krb5" could fail with the following error:
mount error(5): Input/output error
This update corrects the cifs.upcall utility to set the GSSAPI channel bindings properly, and such CIFS shares can now be mounted as expected.
All users of cifs-utils are advised to upgrade to this updated package, which resolves this issue.