[PATCH] NFSD: fix LISTXATTRS returning more bytes than maxcount

[PATCH] NFSD: fix LISTXATTRS returning more bytes than maxcount

[Jorge Mora]

The maxcount is the maximum number of bytes for the LISTXATTRS4resok
result. This includes the cookie and the count for the name array,
thus subtract 12 bytes from the maxcount: 8 (cookie) + 4 (array count)
when filling up the name array.

Fixes: 23e50fe3a5e6 ("nfsd: implement the xattr functions and en/decode logic")
Signed-off-by: Jorge Mora <mora@netapp.com>
---
 fs/nfsd/nfs4xdr.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 92c7dde148a4..17e6404f4296 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -5168,7 +5168,8 @@ nfsd4_encode_listxattrs(struct nfsd4_compoundres *resp, __be32 nfserr,
 	sp = listxattrs->lsxa_buf;
 	nuser = 0;
 
-	xdrleft = listxattrs->lsxa_maxcount;
+	/* Bytes left is maxcount - 8 (cookie) - 4 (array count) */
+	xdrleft = listxattrs->lsxa_maxcount - 12;
 
 	while (left > 0 && xdrleft > 0) {
 		slen = strlen(sp);
-- 
2.43.0

Re: [PATCH] NFSD: fix LISTXATTRS returning more bytes than maxcount

[Jeff Layton]

On Thu, 2024-01-25 at 07:42 -0700, Jorge Mora wrote:
> The maxcount is the maximum number of bytes for the LISTXATTRS4resok
> result. This includes the cookie and the count for the name array,
> thus subtract 12 bytes from the maxcount: 8 (cookie) + 4 (array count)
> when filling up the name array.
> 
> Fixes: 23e50fe3a5e6 ("nfsd: implement the xattr functions and en/decode logic")
> Signed-off-by: Jorge Mora <mora@netapp.com>
> ---
>  fs/nfsd/nfs4xdr.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 92c7dde148a4..17e6404f4296 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -5168,7 +5168,8 @@ nfsd4_encode_listxattrs(struct nfsd4_compoundres *resp, __be32 nfserr,
>  	sp = listxattrs->lsxa_buf;
>  	nuser = 0;
>  
> -	xdrleft = listxattrs->lsxa_maxcount;
> +	/* Bytes left is maxcount - 8 (cookie) - 4 (array count) */
> +	xdrleft = listxattrs->lsxa_maxcount - 12;
>  
>  	while (left > 0 && xdrleft > 0) {
>  		slen = strlen(sp);

Nice catch!

Reviewed-by: Jeff Layton <jlayton@kernel.org>

Re: [PATCH] NFSD: fix LISTXATTRS returning more bytes than maxcount

[Chuck Lever]

On Thu, Jan 25, 2024 at 07:42:23AM -0700, Jorge Mora wrote:
> The maxcount is the maximum number of bytes for the LISTXATTRS4resok
> result. This includes the cookie and the count for the name array,
> thus subtract 12 bytes from the maxcount: 8 (cookie) + 4 (array count)
> when filling up the name array.
> 
> Fixes: 23e50fe3a5e6 ("nfsd: implement the xattr functions and en/decode logic")
> Signed-off-by: Jorge Mora <mora@netapp.com>
> ---
>  fs/nfsd/nfs4xdr.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 92c7dde148a4..17e6404f4296 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -5168,7 +5168,8 @@ nfsd4_encode_listxattrs(struct nfsd4_compoundres *resp, __be32 nfserr,
>  	sp = listxattrs->lsxa_buf;
>  	nuser = 0;
>  
> -	xdrleft = listxattrs->lsxa_maxcount;
> +	/* Bytes left is maxcount - 8 (cookie) - 4 (array count) */
> +	xdrleft = listxattrs->lsxa_maxcount - 12;
>  
>  	while (left > 0 && xdrleft > 0) {
>  		slen = strlen(sp);
> -- 
> 2.43.0
> 

All four applied to nfsd-next.

Note this checkpatch complaint:

WARNING: From:/Signed-off-by: email address mismatch:
  'From: Jorge Mora <jmora1300@gmail.com>' != 'Signed-off-by: Jorge Mora <mora@netapp.com>'

I'm not sure whether that mismatch is a critical problem. These
look like good fixes and b4 says your DKIM is good, so I applied
them anyway.

-- 
Chuck Lever