Re: [PATCH] SUNRPC: improve error response to over-size gss credential

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> On Sep 1, 2021, at 7:30 PM, NeilBrown <neilb@xxxxxxx> wrote:
> 
> 
> When the NFS server receives a large gss (kerberos) credential and tries
> to pass it up to rpc.svcgssd (which is deprecated), it triggers an
> infinite loop in cache_read().
> 
> cache_request() always returns -EAGAIN, and this causes a "goto again".
> 
> This patch:
> - changes the error to -E2BIG to avoid the infinite loop, and
> - generates a WARN_ONCE when rsi_request first sees an over-sized
>   credential.  The warning suggests switching to gssproxy.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=196583
> Signed-off-by: NeilBrown <neilb@xxxxxxx>

Thanks, Neil, I've queued this up for nfsd-5.15-1.


> ---
> net/sunrpc/auth_gss/svcauth_gss.c | 2 ++
> net/sunrpc/cache.c                | 2 +-
> 2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
> index a81be45f40d9..e738c0182f09 100644
> --- a/net/sunrpc/auth_gss/svcauth_gss.c
> +++ b/net/sunrpc/auth_gss/svcauth_gss.c
> @@ -194,6 +194,8 @@ static void rsi_request(struct cache_detail *cd,
> 	qword_addhex(bpp, blen, rsii->in_handle.data, rsii->in_handle.len);
> 	qword_addhex(bpp, blen, rsii->in_token.data, rsii->in_token.len);
> 	(*bpp)[-1] = '\n';
> +	WARN_ONCE(*blen < 0,
> +		  "RPCSEC/GSS credential too large - please use gssproxy\n");
> }
> 
> static int rsi_parse(struct cache_detail *cd,
> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> index 1a2c1c44bb00..59641803472c 100644
> --- a/net/sunrpc/cache.c
> +++ b/net/sunrpc/cache.c
> @@ -803,7 +803,7 @@ static int cache_request(struct cache_detail *detail,
> 
> 	detail->cache_request(detail, crq->item, &bp, &len);
> 	if (len < 0)
> -		return -EAGAIN;
> +		return -E2BIG;
> 	return PAGE_SIZE - len;
> }
> 
> -- 
> 2.32.0
> 

--
Chuck Lever







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