nfsd: don't ignore the return code of svc_proc_register()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: don't ignore the return code of svc_proc_register() Currently, nfsd_proc_stat_init() ignores the return value of svc_proc_register(). If the procfile creation fails, then the kernel will WARN when it tries to remove the entry later. Fix nfsd_proc_stat_init() to return the same type of pointer as svc_proc_register(), and fix up nfsd_net_init() to check that and fail the nfsd_net construction if it occurs. svc_proc_register() can fail if the dentry can't be allocated, or if an identical dentry already exists. The second case is pretty unlikely in the nfsd_net construction codepath, so if this happens, return -ENOMEM.

References

• https://git.kernel.org/stable/c/51107e768de6821b68aa34a136d07bc7a09cf6c3
• https://git.kernel.org/stable/c/e4316bd85e42b01125b2aab691769234a388b8a3
• https://git.kernel.org/stable/c/51da899c209a9624e48be416bd30e7ed5cd6c3d8
• https://git.kernel.org/stable/c/30405b23b4d5e2a596fb756d48119d7293194e75
• https://git.kernel.org/stable/c/6a59b70fe71ec66c0dd19e2c279c71846a3fb2f0
• https://git.kernel.org/stable/c/e31957a819e60cf0bc9a49408765e6095fd3d046
• https://git.kernel.org/stable/c/9d9456185fd5f1891c74354ee297f19538141ead
• https://git.kernel.org/stable/c/930b64ca0c511521f0abdd1d57ce52b2a6e3476b