patch "VMCI: fix NULL pointer dereference when unmapping queue pair" added to char-misc-testing

This is a note to let you know that I've just added the patch titled

VMCI: fix NULL pointer dereference when unmapping queue pair

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-testing branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will be merged to the char-misc-next branch sometime soon, after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.

From a30dc6cf0dc51419021550152e435736aaef8799 Mon Sep 17 00:00:00 2001
From: Wang Hai <[email protected]>
Date: Wed, 18 Aug 2021 20:48:45 +0800
Subject: VMCI: fix NULL pointer dereference when unmapping queue pair

I got a NULL pointer dereference report when doing fuzz test:

Call Trace:
  qp_release_pages+0xae/0x130
  qp_host_unregister_user_memory.isra.25+0x2d/0x80
  vmci_qp_broker_unmap+0x191/0x320
  ? vmci_host_do_alloc_queuepair.isra.9+0x1c0/0x1c0
  vmci_host_unlocked_ioctl+0x59f/0xd50
  ? do_vfs_ioctl+0x14b/0xa10
  ? tomoyo_file_ioctl+0x28/0x30
  ? vmci_host_do_alloc_queuepair.isra.9+0x1c0/0x1c0
  __x64_sys_ioctl+0xea/0x120
  do_syscall_64+0x34/0xb0
  entry_SYSCALL_64_after_hwframe+0x44/0xae

When a queue pair is created by the following call, it will not register the user memory if the page_store is NULL, and the entry->state will be set to VMCIQPB_CREATED_NO_MEM.

vmci_host_unlocked_ioctl
vmci_host_do_alloc_queuepair

    vmci_qp_broker_alloc
      qp_broker_alloc
        qp_broker_create // set entry->state = VMCIQPB_CREATED_NO_MEM;

When unmapping this queue pair, qp_host_unregister_user_memory() will be called to unregister the non-existent user memory, which will result in a null pointer reference. It will also change VMCIQPB_CREATED_NO_MEM to VMCIQPB_CREATED_MEM, which should not be present in this operation.

Only when the qp broker has mem, it can unregister the user memory when unmapping the qp broker.

Only when the qp broker has no mem, it can register the user memory when mapping the qp broker.

---
 drivers/misc/vmw_vmci/vmci_queue_pair.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index 880c33ab9f47..94ebf7f3fd58 100644
@@ -2243,7 +2243,8 @@ int vmci_qp_broker_map(struct vmci_handle handle,
 
 	result = VMCI_SUCCESS;
 
-	if (context_id != VMCI_HOST_CONTEXT_ID) {
+	if (context_id != VMCI_HOST_CONTEXT_ID &&
+	    !QPBROKERSTATE_HAS_MEM(entry)) {
 		struct vmci_qp_page_store page_store;
 
 		page_store.pages = guest_mem;

@@ -2350,7 +2351,8 @@ int vmci_qp_broker_unmap(struct vmci_handle handle,
 		goto out;
 	}
 
-	if (context_id != VMCI_HOST_CONTEXT_ID) {
+	if (context_id != VMCI_HOST_CONTEXT_ID &&
+	    QPBROKERSTATE_HAS_MEM(entry)) {
 		qp_acquire_queue_mutex(entry->produce_q);
 		result = qp_save_headers(entry);
 		if (result < VMCI_SUCCESS)

2.32.0