linux-kernel - Re: [PATCH] nfs: Fix fscache volume key rendering for endianness

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Date:   Thu, 19 May 2022 14:01:57 -0400
From:   David Wysochanski <dwysocha@...hat.com>
To:     David Howells <dhowells@...hat.com>
Cc:     Trond Myklebust <trond.myklebust@...merspace.com>, anna@...nel.org,
        Jeff Layton <jlayton@...nel.org>,
        linux-nfs <linux-nfs@...r.kernel.org>,
        linux-cachefs <linux-cachefs@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nfs: Fix fscache volume key rendering for endianness

On Thu, May 19, 2022 at 3:51 AM David Howells <dhowells@...hat.com> wrote:
>
> Fix fscache volume key rendering for endianness.  Convert the BE numbers in
> the address to host-endian before printing them so that they're consistent
> if the cache is copied between architectures.
>
> Question: This change could lead to misidentification of a volume directory
> in the cache on a LE machine (it's unlikely because the port number as well
> as the address numbers all get flipped), but it was introduced in -rc1 in
> this cycle so probably isn't in any distro kernels yet.  Should I add a
> version number to enforce non-matching?
>
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: Dave Wysochanski <dwysocha@...hat.com>
> cc: Trond Myklebust <trond.myklebust@...merspace.com>
> cc: Anna Schumaker <anna@...nel.org>
> cc: Jeff Layton <jlayton@...nel.org>
> cc: linux-nfs@...r.kernel.org
> cc: linux-cachefs@...hat.com
> ---
>
>  fs/nfs/fscache.c |   14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c
> index f73c09a9cf0a..0e5572b192b2 100644
> --- a/fs/nfs/fscache.c
> +++ b/fs/nfs/fscache.c
> @@ -54,17 +54,17 @@ static bool nfs_fscache_get_client_key(struct nfs_client *clp,
>
>         switch (clp->cl_addr.ss_family) {
>         case AF_INET:
> -               if (!nfs_append_int(key, _len, sin->sin_port) ||
> -                   !nfs_append_int(key, _len, sin->sin_addr.s_addr))
> +               if (!nfs_append_int(key, _len, ntohs(sin->sin_port)) ||
> +                   !nfs_append_int(key, _len, ntohl(sin->sin_addr.s_addr)))
>                         return false;
>                 return true;
>
>         case AF_INET6:
> -               if (!nfs_append_int(key, _len, sin6->sin6_port) ||
> -                   !nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[0]) ||
> -                   !nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[1]) ||
> -                   !nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[2]) ||
> -                   !nfs_append_int(key, _len, sin6->sin6_addr.s6_addr32[3]))
> +               if (!nfs_append_int(key, _len, ntohs(sin6->sin6_port)) ||
> +                   !nfs_append_int(key, _len, ntohl(sin6->sin6_addr.s6_addr32[0])) ||
> +                   !nfs_append_int(key, _len, ntohl(sin6->sin6_addr.s6_addr32[1])) ||
> +                   !nfs_append_int(key, _len, ntohl(sin6->sin6_addr.s6_addr32[2])) ||
> +                   !nfs_append_int(key, _len, ntohl(sin6->sin6_addr.s6_addr32[3])))
>                         return false;
>                 return true;
>
>
>

IMO it's not worth versioning in this case but I agree with this change.
Did someone report the "cache copied between architectures" issue, or
is that mostly a theoretical problem you noticed?

Acked-by: Dave Wysochanski <dwysocha@...hat.com>