Re: [syzbot] [kernel?] KMSAN: kernel-infoleak in vmci_host_unlocked_ioctl (3)

[Hillf Danton]

On Thu, 19 Jun 2025 16:57:26 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    08215f5486ec Merge tag 'kbuild-fixes-v6.16' of git://git.k..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=13f7fd70580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=61539536677af51c
> dashboard link: https://syzkaller.appspot.com/bug?extid=9b9124ae9b12d5af5d95
> compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f7fd70580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1485690c580000

#syz test

--- x/drivers/misc/vmw_vmci/vmci_context.c
+++ y/drivers/misc/vmw_vmci/vmci_context.c
@@ -535,6 +535,7 @@ int vmci_ctx_dequeue_datagram(struct vmc
 			 (u32) *max_size);
 		return VMCI_ERROR_NO_MEM;
 	}
+	*max_size = dq_entry->dg_size;
 
 	list_del(list_item);
 	context->pending_datagrams--;
--- x/drivers/misc/vmw_vmci/vmci_host.c
+++ y/drivers/misc/vmw_vmci/vmci_host.c
@@ -435,7 +435,7 @@ static int vmci_host_do_receive_datagram
 
 	if (recv_info.result >= VMCI_SUCCESS) {
 		void __user *ubuf = (void __user *)(uintptr_t)recv_info.addr;
-		retval = copy_to_user(ubuf, dg, VMCI_DG_SIZE(dg));
+		retval = copy_to_user(ubuf, dg, size);
 		kfree(dg);
 		if (retval != 0)
 			return -EFAULT;
--