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Fixing two (somewhat rare) endpoint-related race issues, both of which 

were reported by Fernando Guzman Lugo.
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Merge tag 'rpmsg-3.5-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ohad/rpmsg

Pull rpmsg fixes from Ohad Ben-Cohen:
 "Fixing two (somewhat rare) endpoint-related race issues, both of which
  were reported by Fernando Guzman Lugo."

* tag 'rpmsg-3.5-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ohad/rpmsg:
  rpmsg: make sure inflight messages don't invoke just-removed callbacks
  rpmsg: avoid premature deallocation of endpoints
This commit is contained in:
Linus Torvalds 2012-07-09 13:24:00 -07:00
parent 84836bf973 15fd943af5
commit 6f5410b688
2 changed files with 56 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

55
drivers/rpmsg/virtio_rpmsg_bus.c
View File

@ -188,6 +188,26 @@ static int rpmsg_uevent(struct device *dev, struct kobj_uevent_env *env)
rpdev->id.name);
}
/**
* __ept_release() - deallocate an rpmsg endpoint
* @kref: the ept's reference count
*
* This function deallocates an ept, and is invoked when its @kref refcount
* drops to zero.
*
* Never invoke this function directly!
*/
static void __ept_release(struct kref *kref)
{
struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
refcount);
/*
* At this point no one holds a reference to ept anymore,
* so we can directly free it
*/
kfree(ept);
}
/* for more info, see below documentation of rpmsg_create_ept() */
static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
struct rpmsg_channel *rpdev, rpmsg_rx_cb_t cb,
@ -206,6 +226,9 @@ static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
return NULL;
}
kref_init(&ept->refcount);
mutex_init(&ept->cb_lock);
ept->rpdev = rpdev;
ept->cb = cb;
ept->priv = priv;
@ -238,7 +261,7 @@ rem_idr:
idr_remove(&vrp->endpoints, request);
free_ept:
mutex_unlock(&vrp->endpoints_lock);
kfree(ept);
kref_put(&ept->refcount, __ept_release);
return NULL;
}
@ -302,11 +325,17 @@ EXPORT_SYMBOL(rpmsg_create_ept);
static void
__rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
{
/* make sure new inbound messages can't find this ept anymore */
mutex_lock(&vrp->endpoints_lock);
idr_remove(&vrp->endpoints, ept->addr);
mutex_unlock(&vrp->endpoints_lock);
kfree(ept);
/* make sure in-flight inbound messages won't invoke cb anymore */
mutex_lock(&ept->cb_lock);
ept->cb = NULL;
mutex_unlock(&ept->cb_lock);
kref_put(&ept->refcount, __ept_release);
}
/**
@ -790,12 +819,28 @@ static void rpmsg_recv_done(struct virtqueue *rvq)
/* use the dst addr to fetch the callback of the appropriate user */
mutex_lock(&vrp->endpoints_lock);
ept = idr_find(&vrp->endpoints, msg->dst);
/* let's make sure no one deallocates ept while we use it */
if (ept)
kref_get(&ept->refcount);
mutex_unlock(&vrp->endpoints_lock);
if (ept && ept->cb)
ept->cb(ept->rpdev, msg->data, msg->len, ept->priv, msg->src);
else
if (ept) {
/* make sure ept->cb doesn't go away while we use it */
mutex_lock(&ept->cb_lock);
if (ept->cb)
ept->cb(ept->rpdev, msg->data, msg->len, ept->priv,
msg->src);
mutex_unlock(&ept->cb_lock);
/* farewell, ept, we don't need you anymore */
kref_put(&ept->refcount, __ept_release);
} else
dev_warn(dev, "msg received with no recepient\n");
/* publish the real size of the buffer */

6
include/linux/rpmsg.h
View File

@ -38,6 +38,8 @@
#include <linux/types.h>
#include <linux/device.h>
#include <linux/mod_devicetable.h>
#include <linux/kref.h>
#include <linux/mutex.h>
/* The feature bitmap for virtio rpmsg */
#define VIRTIO_RPMSG_F_NS 0 /* RP supports name service notifications */
@ -120,7 +122,9 @@ typedef void (*rpmsg_rx_cb_t)(struct rpmsg_channel *, void *, int, void *, u32);
/**
* struct rpmsg_endpoint - binds a local rpmsg address to its user
* @rpdev: rpmsg channel device
* @refcount: when this drops to zero, the ept is deallocated
* @cb: rx callback handler
* @cb_lock: must be taken before accessing/changing @cb
* @addr: local rpmsg address
* @priv: private data for the driver's use
*
@ -140,7 +144,9 @@ typedef void (*rpmsg_rx_cb_t)(struct rpmsg_channel *, void *, int, void *, u32);
*/
struct rpmsg_endpoint {
struct rpmsg_channel *rpdev;
struct kref refcount;
rpmsg_rx_cb_t cb;
struct mutex cb_lock;
u32 addr;
void *priv;
};