[Qemu-devel] [PATCH 1/2] nbd: do not check request length except for reads and writes

[Paolo Bonzini <pbonzini@redhat.com>]

Only reads and writes need to allocate memory correspondent to the
request length.  Other requests can be sent to the storage without
allocating any memory, and thus any request length is acceptable.

Reported-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Cc: qemu-block@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 nbd.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/nbd.c b/nbd.c
index b3d9654..e395a16 100644
--- a/nbd.c
+++ b/nbd.c
@@ -1227,13 +1227,6 @@ static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *reque
         goto out;
     }
 
-    if (request->len > NBD_MAX_BUFFER_SIZE) {
-        LOG("len (%u) is larger than max len (%u)",
-            request->len, NBD_MAX_BUFFER_SIZE);
-        rc = -EINVAL;
-        goto out;
-    }
-
     if ((request->from + request->len) < request->from) {
         LOG("integer overflow detected! "
             "you're probably being attacked");
@@ -1245,6 +1238,13 @@ static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *reque
 
     command = request->type & NBD_CMD_MASK_COMMAND;
     if (command == NBD_CMD_READ || command == NBD_CMD_WRITE) {
+        if (request->len > NBD_MAX_BUFFER_SIZE) {
+            LOG("len (%u) is larger than max len (%u)",
+                request->len, NBD_MAX_BUFFER_SIZE);
+            rc = -EINVAL;
+            goto out;
+        }
+
         req->data = blk_blockalign(client->exp->blk, request->len);
     }
     if (command == NBD_CMD_WRITE) {
-- 
2.5.0