On Mon, Feb 21, 2022 at 12:58:51PM +0530, Anirudh Rayabharam wrote:
Return early when userspace sends zero regions in the VHOST_SET_MEM_TABLE ioctl. Otherwise, this causes an erroneous entry to be added to the iotlb. This entry has a range size of 0 (due to u64 overflow). This then causes iotlb_access_ok() to loop indefinitely resulting in a hung thread. Syzbot has reported this here: https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
IIUC vhost_iotlb_add_range() in the for loop is never called if mem.nregions is 0, so I'm not sure the problem reported by syzbot is related.
In any case maybe this patch is fine, but currently I think we're just registering an iotlb without any regions, which in theory shouldn't cause any problems.
Thanks, Stefano
Reported-and-tested-by: syzbot+0abd373e2e50d704db87@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Anirudh Rayabharam <mail@xxxxxxxxxxxxx> --- drivers/vhost/vhost.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 59edb5a1ffe2..821aba60eac2 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1428,6 +1428,8 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m) return -EFAULT; if (mem.padding) return -EOPNOTSUPP; + if (mem.nregions == 0) + return 0; if (mem.nregions > max_mem_regions) return -E2BIG; newmem = kvzalloc(struct_size(newmem, regions, mem.nregions), -- 2.35.1
