[PATCH v2 02/23] NFSv4/pnfs: bound the CB_NOTIFY_DEVICEID array count before allocating

decode_devicenotify_args() hands the server's notification count
straight to kmalloc_objs() as the array length, without checking it
against the message that carried it.  Bound it the way nfs4xdr.c bounds
an attribute length, against xdr_stream_remaining().

Fixes: 1be5683b03a7 ("pnfs: CB_NOTIFY_DEVICEID")
Cc: [email protected]
Assisted-by: Claude:claude-fable-5
Signed-off-by: Benjamin Coddington <[email protected]>
---
 fs/nfs/callback_xdr.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
index 4382baddc9ee..2d3d0f237ba1 100644
--- a/fs/nfs/callback_xdr.c
+++ b/fs/nfs/callback_xdr.c
@@ -271,6 +271,13 @@ __be32 decode_devicenotify_args(struct svc_rqst *rqstp,
 	if (n == 0)
 		goto out;
 
+	/* sanity check the count against the remaining stream */
+	if (n > xdr_stream_remaining(xdr) /
+		((4 * sizeof(uint32_t)) + NFS4_DEVICEID4_SIZE)) {
+		status = htonl(NFS4ERR_BADXDR);
+		goto out;
+	}
+
 	args->devs = kmalloc_objs(*args->devs, n);
 	if (!args->devs) {
 		status = htonl(NFS4ERR_DELAY);
-- 
2.53.0