vringh: Use wiov->used to check for read/write desc order
mainline inclusion from mainline-5.10.62 commit c7ee4d22614e43ae1d633864b70ac075469ad27f bugzilla: 182217 https://gitee.com/openeuler/kernel/issues/I4EFOS Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c7ee4d22614e43ae1d633864b70ac075469ad27f -------------------------------- [ Upstream commit e74cfa91 ] As __vringh_iov() traverses a descriptor chain, it populates each descriptor entry into either read or write vring iov and increments that iov's ->used member. So, as we iterate over a descriptor chain, at any point, (riov/wriov)->used value gives the number of descriptor enteries available, which are to be read or written by the device. As all read iovs must precede the write iovs, wiov->used should be zero when we are traversing a read descriptor. Current code checks for wiov->i, to figure out whether any previous entry in the current descriptor chain was a write descriptor. However, iov->i is only incremented, when these vring iovs are consumed, at a later point, and remain 0 in __vringh_iov(). So, correct the check for read and write descriptor order, to use wiov->used. Acked-by: NJason Wang <jasowang@redhat.com> Reviewed-by: NStefano Garzarella <sgarzare@redhat.com> Signed-off-by: NNeeraj Upadhyay <neeraju@codeaurora.org> Link: https://lore.kernel.org/r/1624591502-4827-1-git-send-email-neeraju@codeaurora.orgSigned-off-by: NMichael S. Tsirkin <mst@redhat.com> Signed-off-by: NSasha Levin <sashal@kernel.org> Signed-off-by: NChen Jun <chenjun102@huawei.com> Acked-by: NWeilong Chen <chenweilong@huawei.com> Signed-off-by: NChen Jun <chenjun102@huawei.com> Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
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