NFSD: prevent underflow in nfssvc_decode_writeargs()

stable inclusion
from stable-v5.10.110
commit 65e21cc042f4c1518c8c55283f53bc725b78419d
bugzilla: https://gitee.com/openeuler/kernel/issues/I574AL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=65e21cc042f4c1518c8c55283f53bc725b78419d

--------------------------------

commit 184416d4 upstream.

Smatch complains:

	fs/nfsd/nfsxdr.c:341 nfssvc_decode_writeargs()
	warn: no lower bound on 'args->len'

Change the type to unsigned to prevent this issue.

Cc: stable@vger.kernel.org
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NChuck Lever <chuck.lever@oracle.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/nfsd/nfsproc.c

@@ -223,7 +223,7 @@ nfsd_proc_write(struct svc_rqst *rqstp)
 	unsigned long cnt = argp->len;
 	unsigned int nvecs;
 
-	dprintk("nfsd: WRITE    %s %d bytes at %d\n",
+	dprintk("nfsd: WRITE    %s %u bytes at %d\n",
 		SVCFH_fmt(&argp->fh),
 		argp->len, argp->offset);
 

fs/nfsd/xdr.h

@@ -33,7 +33,7 @@ struct nfsd_readargs {
 struct nfsd_writeargs {
 	svc_fh			fh;
 	__u32			offset;
-	int			len;
+	__u32			len;
 	struct kvec		first;
 };