git: 3fe2c68ba20f - main - nfsclient: fix panic in cache_enter_time()

[Konstantin Belousov]

On Sun, Feb 28, 2021 at 01:56:43AM +0000, Rick Macklem wrote:
> The branch main has been updated by rmacklem:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=3fe2c68ba20fb3365ef91e0b85f88237b5369f38
> 
> commit 3fe2c68ba20fb3365ef91e0b85f88237b5369f38
> Author:     Rick Macklem <rmacklem at FreeBSD.org>
> AuthorDate: 2021-02-28 01:54:05 +0000
> Commit:     Rick Macklem <rmacklem at FreeBSD.org>
> CommitDate: 2021-02-28 01:54:05 +0000
> 
>     nfsclient: fix panic in cache_enter_time()
>     
>     Juraj Lutter (otis@) reported a panic "dvp != vp not true" in
>     cache_enter_time() called from the NFS client's nfsrpc_readdirplus()
>     function.
>     This is specific to an NFSv3 mount with the "rdirplus" mount
>     option. Unlike NFSv4, NFSv3 replies to ReaddirPlus
>     includes entries for the current directory.

Should we check cache_enterXXX() args for other places, like lookup,
as well?  Malicious or buggy server could return the vp == dvp even for
case other than dot.

BTW, for some cases, dotdot can result in dvp == vp as well.