genetlink: fix genl_bind() invoking bind() after -EPERM

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: genetlink: fix genl_bind() invoking bind() after -EPERM Per family bind/unbind callbacks were introduced to allow families to track multicast group consumer presence, e.g. to start or stop producing events depending on listeners. However, in genl_bind() the bind() callback was invoked even if capability checks failed and ret was set to -EPERM. This means that callbacks could run on behalf of unauthorized callers while the syscall still returned failure to user space. Fix this by only invoking bind() after "if (ret) break;" check i.e. after permission checks have succeeded.

References

• https://git.kernel.org/stable/c/98c9d884047a3051c203708914a874dece3cbe54
• https://git.kernel.org/stable/c/8858c1e9405906c09589d7c336f04058ea198207
• https://git.kernel.org/stable/c/1dbfb0363224f6da56f6655d596dc5097308d6f5