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 the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: vmci-fix-null-pointer-dereference-when-unmapping-queue-pair.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From a30dc6cf0dc51419021550152e435736aaef8799 Mon Sep 17 00:00:00 2001 From: Wang Hai <wanghai38@xxxxxxxxxx> Date: Wed, 18 Aug 2021 20:48:45 +0800 Subject: VMCI: fix NULL pointer dereference when unmapping queue pair From: Wang Hai <wanghai38@xxxxxxxxxx> commit a30dc6cf0dc51419021550152e435736aaef8799 upstream. 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. Fixes: 06164d2b72aa ("VMCI: queue pairs implementation.") Cc: stable <stable@xxxxxxxxxxxxxxx> Reported-by: Hulk Robot <hulkci@xxxxxxxxxx> Reviewed-by: Jorgen Hansen <jhansen@xxxxxxxxxx> Signed-off-by: Wang Hai <wanghai38@xxxxxxxxxx> Link: https://lore.kernel.org/r/20210818124845.488312-1-wanghai38@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/misc/vmw_vmci/vmci_queue_pair.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/drivers/misc/vmw_vmci/vmci_queue_pair.c +++ b/drivers/misc/vmw_vmci/vmci_queue_pair.c @@ -2344,7 +2344,8 @@ int vmci_qp_broker_map(struct vmci_handl is_local = entry->qp.flags & VMCI_QPFLAG_LOCAL; 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; @@ -2454,7 +2455,8 @@ int vmci_qp_broker_unmap(struct vmci_han is_local = entry->qp.flags & VMCI_QPFLAG_LOCAL; - 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) Patches currently in stable-queue which might be from wanghai38@xxxxxxxxxx are queue-4.9/vmci-fix-null-pointer-dereference-when-unmapping-queue-pair.patch