[PATCH 4.14 07/44] NFSD: Clamp WRITE offsets

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Chuck Lever <chuck.lever@oracle.com>

commit 6260d9a56ab352b54891ec66ab0eced57d55abc6 upstream.

Ensure that a client cannot specify a WRITE range that falls in a
byte range outside what the kernel's internal types (such as loff_t,
which is signed) can represent. The kiocb iterators, invoked in
nfsd_vfs_write(), should properly limit write operations to within
the underlying file system's s_maxbytes.

Cc: stable@vger.kernel.org
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/nfsd/nfs3proc.c |    5 +++++
 fs/nfsd/nfs4proc.c |    5 +++--
 2 files changed, 8 insertions(+), 2 deletions(-)

--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -199,6 +199,11 @@ nfsd3_proc_write(struct svc_rqst *rqstp)
 				(unsigned long long) argp->offset,
 				argp->stable? " stable" : "");
 
+	resp->status = nfserr_fbig;
+	if (argp->offset > (u64)OFFSET_MAX ||
+	    argp->offset + argp->len > (u64)OFFSET_MAX)
+		return rpc_success;
+
 	fh_copy(&resp->fh, &argp->fh);
 	resp->committed = argp->stable;
 	nfserr = nfsd_write(rqstp, &resp->fh, argp->offset,
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1015,8 +1015,9 @@ nfsd4_write(struct svc_rqst *rqstp, stru
 	unsigned long cnt;
 	int nvecs;
 
-	if (write->wr_offset >= OFFSET_MAX)
-		return nfserr_inval;
+	if (write->wr_offset > (u64)OFFSET_MAX ||
+	    write->wr_offset + write->wr_buflen > (u64)OFFSET_MAX)
+		return nfserr_fbig;
 
 	status = nfs4_preprocess_stateid_op(rqstp, cstate, &cstate->current_fh,
 						stateid, WR_STATE, &filp, NULL);