In the Linux kernel, the following vulnerability has been resolved: vhost: fix hung thread due to erroneous iotlb entries In vhostiotlbaddrangectx(), range size can overflow to 0 when start is 0 and last is ULONGMAX. One instance where it can happen is when userspace sends an IOTLB message with iova=size=uaddr=0 (vhostprocessiotlbmsg). So, an entry with size = 0, start = 0, last = ULONGMAX ends up in the iotlb. Next time a packet is sent, iotlbaccessok() loops indefinitely due to that erroneous entry. Call Trace: <TASK> iotlbaccessok+0x21b/0x3e0 drivers/vhost/vhost.c:1340 vqmetaprefetch+0xbc/0x280 drivers/vhost/vhost.c:1366 vhosttransportdosendpkt+0xe0/0xfd0 drivers/vhost/vsock.c:104 vhostworker+0x23d/0x3d0 drivers/vhost/vhost.c:372 kthread+0x2e9/0x3a0 kernel/kthread.c:377 retfromfork+0x1f/0x30 arch/x86/entry/entry64.S:295 </TASK> Reported by syzbot at: https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87 To fix this, do two things: 1. Return -EINVAL in vhostchrwriteiter() when userspace asks to map a range with size 0. 2. Fix vhostiotlbaddrangectx() to handle the range [0, ULONG_MAX] by splitting it into two entries.
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