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![Michael S. Tsirkin](/assets/img/avatar_default.png)
The ring element addresses are passed between components with different alignments assumptions. Thus, if guest/userspace selects a pointer and host then gets and dereferences it, we might need to decrease the compiler-selected alignment to prevent compiler on the host from assuming pointer is aligned. This actually triggers on ARM with -mabi=apcs-gnu - which is a deprecated configuration, but it seems safer to handle this generally. Note that userspace that allocates the memory is actually OK and does not need to be fixed, but userspace that gets it from guest or another process does need to be fixed. The later doesn't generally talk to the kernel so while it might be buggy it's not talking to the kernel in the buggy way - it's just using the header in the buggy way - so fixing header and asking userspace to recompile is the best we can do. I verified that the produced kernel binary on x86 is exactly identical before and after the change. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com>
293 lines
8.3 KiB
C
293 lines
8.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* Linux host-side vring helpers; for when the kernel needs to access
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* someone else's vring.
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*
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* Copyright IBM Corporation, 2013.
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* Parts taken from drivers/vhost/vhost.c Copyright 2009 Red Hat, Inc.
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*
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* Written by: Rusty Russell <rusty@rustcorp.com.au>
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*/
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#ifndef _LINUX_VRINGH_H
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#define _LINUX_VRINGH_H
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#include <uapi/linux/virtio_ring.h>
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#include <linux/virtio_byteorder.h>
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#include <linux/uio.h>
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#include <linux/slab.h>
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#if IS_REACHABLE(CONFIG_VHOST_IOTLB)
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#include <linux/dma-direction.h>
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#include <linux/vhost_iotlb.h>
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#endif
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#include <asm/barrier.h>
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/* virtio_ring with information needed for host access. */
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struct vringh {
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/* Everything is little endian */
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bool little_endian;
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/* Guest publishes used event idx (note: we always do). */
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bool event_indices;
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/* Can we get away with weak barriers? */
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bool weak_barriers;
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/* Last available index we saw (ie. where we're up to). */
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u16 last_avail_idx;
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/* Last index we used. */
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u16 last_used_idx;
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/* How many descriptors we've completed since last need_notify(). */
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u32 completed;
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/* The vring (note: it may contain user pointers!) */
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struct vring vring;
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/* IOTLB for this vring */
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struct vhost_iotlb *iotlb;
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/* The function to call to notify the guest about added buffers */
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void (*notify)(struct vringh *);
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};
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/**
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* struct vringh_config_ops - ops for creating a host vring from a virtio driver
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* @find_vrhs: find the host vrings and instantiate them
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* vdev: the virtio_device
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* nhvrs: the number of host vrings to find
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* hvrs: on success, includes new host vrings
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* callbacks: array of driver callbacks, for each host vring
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* include a NULL entry for vqs that do not need a callback
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* Returns 0 on success or error status
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* @del_vrhs: free the host vrings found by find_vrhs().
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*/
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struct virtio_device;
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typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
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struct vringh_config_ops {
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int (*find_vrhs)(struct virtio_device *vdev, unsigned nhvrs,
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struct vringh *vrhs[], vrh_callback_t *callbacks[]);
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void (*del_vrhs)(struct virtio_device *vdev);
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};
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/* The memory the vring can access, and what offset to apply. */
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struct vringh_range {
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u64 start, end_incl;
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u64 offset;
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};
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/**
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* struct vringh_iov - iovec mangler.
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*
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* Mangles iovec in place, and restores it.
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* Remaining data is iov + i, of used - i elements.
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*/
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struct vringh_iov {
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struct iovec *iov;
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size_t consumed; /* Within iov[i] */
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unsigned i, used, max_num;
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};
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/**
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* struct vringh_iov - kvec mangler.
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*
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* Mangles kvec in place, and restores it.
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* Remaining data is iov + i, of used - i elements.
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*/
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struct vringh_kiov {
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struct kvec *iov;
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size_t consumed; /* Within iov[i] */
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unsigned i, used, max_num;
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};
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/* Flag on max_num to indicate we're kmalloced. */
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#define VRINGH_IOV_ALLOCATED 0x8000000
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/* Helpers for userspace vrings. */
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int vringh_init_user(struct vringh *vrh, u64 features,
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unsigned int num, bool weak_barriers,
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vring_desc_t __user *desc,
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vring_avail_t __user *avail,
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vring_used_t __user *used);
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static inline void vringh_iov_init(struct vringh_iov *iov,
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struct iovec *iovec, unsigned num)
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{
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iov->used = iov->i = 0;
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iov->consumed = 0;
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iov->max_num = num;
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iov->iov = iovec;
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}
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static inline void vringh_iov_reset(struct vringh_iov *iov)
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{
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iov->iov[iov->i].iov_len += iov->consumed;
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iov->iov[iov->i].iov_base -= iov->consumed;
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iov->consumed = 0;
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iov->i = 0;
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}
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static inline void vringh_iov_cleanup(struct vringh_iov *iov)
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{
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if (iov->max_num & VRINGH_IOV_ALLOCATED)
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kfree(iov->iov);
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iov->max_num = iov->used = iov->i = iov->consumed = 0;
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iov->iov = NULL;
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}
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/* Convert a descriptor into iovecs. */
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int vringh_getdesc_user(struct vringh *vrh,
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struct vringh_iov *riov,
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struct vringh_iov *wiov,
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bool (*getrange)(struct vringh *vrh,
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u64 addr, struct vringh_range *r),
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u16 *head);
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/* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */
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ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len);
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/* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */
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ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
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const void *src, size_t len);
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/* Mark a descriptor as used. */
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int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
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int vringh_complete_multi_user(struct vringh *vrh,
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const struct vring_used_elem used[],
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unsigned num_used);
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/* Pretend we've never seen descriptor (for easy error handling). */
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void vringh_abandon_user(struct vringh *vrh, unsigned int num);
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/* Do we need to fire the eventfd to notify the other side? */
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int vringh_need_notify_user(struct vringh *vrh);
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bool vringh_notify_enable_user(struct vringh *vrh);
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void vringh_notify_disable_user(struct vringh *vrh);
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/* Helpers for kernelspace vrings. */
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int vringh_init_kern(struct vringh *vrh, u64 features,
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unsigned int num, bool weak_barriers,
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struct vring_desc *desc,
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struct vring_avail *avail,
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struct vring_used *used);
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static inline void vringh_kiov_init(struct vringh_kiov *kiov,
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struct kvec *kvec, unsigned num)
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{
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kiov->used = kiov->i = 0;
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kiov->consumed = 0;
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kiov->max_num = num;
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kiov->iov = kvec;
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}
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static inline void vringh_kiov_reset(struct vringh_kiov *kiov)
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{
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kiov->iov[kiov->i].iov_len += kiov->consumed;
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kiov->iov[kiov->i].iov_base -= kiov->consumed;
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kiov->consumed = 0;
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kiov->i = 0;
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}
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static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov)
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{
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if (kiov->max_num & VRINGH_IOV_ALLOCATED)
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kfree(kiov->iov);
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kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0;
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kiov->iov = NULL;
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}
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int vringh_getdesc_kern(struct vringh *vrh,
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struct vringh_kiov *riov,
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struct vringh_kiov *wiov,
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u16 *head,
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gfp_t gfp);
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ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
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ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
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const void *src, size_t len);
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void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
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int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
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bool vringh_notify_enable_kern(struct vringh *vrh);
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void vringh_notify_disable_kern(struct vringh *vrh);
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int vringh_need_notify_kern(struct vringh *vrh);
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/* Notify the guest about buffers added to the used ring */
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static inline void vringh_notify(struct vringh *vrh)
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{
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if (vrh->notify)
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vrh->notify(vrh);
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}
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static inline bool vringh_is_little_endian(const struct vringh *vrh)
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{
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return vrh->little_endian ||
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virtio_legacy_is_little_endian();
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}
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static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)
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{
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return __virtio16_to_cpu(vringh_is_little_endian(vrh), val);
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}
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static inline __virtio16 cpu_to_vringh16(const struct vringh *vrh, u16 val)
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{
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return __cpu_to_virtio16(vringh_is_little_endian(vrh), val);
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}
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static inline u32 vringh32_to_cpu(const struct vringh *vrh, __virtio32 val)
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{
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return __virtio32_to_cpu(vringh_is_little_endian(vrh), val);
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}
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static inline __virtio32 cpu_to_vringh32(const struct vringh *vrh, u32 val)
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{
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return __cpu_to_virtio32(vringh_is_little_endian(vrh), val);
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}
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static inline u64 vringh64_to_cpu(const struct vringh *vrh, __virtio64 val)
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{
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return __virtio64_to_cpu(vringh_is_little_endian(vrh), val);
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}
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static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val)
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{
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return __cpu_to_virtio64(vringh_is_little_endian(vrh), val);
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}
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#if IS_REACHABLE(CONFIG_VHOST_IOTLB)
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void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb);
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int vringh_init_iotlb(struct vringh *vrh, u64 features,
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unsigned int num, bool weak_barriers,
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struct vring_desc *desc,
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struct vring_avail *avail,
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struct vring_used *used);
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int vringh_getdesc_iotlb(struct vringh *vrh,
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struct vringh_kiov *riov,
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struct vringh_kiov *wiov,
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u16 *head,
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gfp_t gfp);
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ssize_t vringh_iov_pull_iotlb(struct vringh *vrh,
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struct vringh_kiov *riov,
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void *dst, size_t len);
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ssize_t vringh_iov_push_iotlb(struct vringh *vrh,
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struct vringh_kiov *wiov,
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const void *src, size_t len);
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void vringh_abandon_iotlb(struct vringh *vrh, unsigned int num);
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int vringh_complete_iotlb(struct vringh *vrh, u16 head, u32 len);
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bool vringh_notify_enable_iotlb(struct vringh *vrh);
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void vringh_notify_disable_iotlb(struct vringh *vrh);
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int vringh_need_notify_iotlb(struct vringh *vrh);
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#endif /* CONFIG_VHOST_IOTLB */
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#endif /* _LINUX_VRINGH_H */
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