linux/drivers/md/dm-log-userspace-transfer.c
Jonathan Brassow ebfd32bba9 dm log: userspace fix overhead_size calcuations
This patch fixes two bugs that revolve around the miscalculation and
misuse of the variable 'overhead_size'.  'overhead_size' is the size of
the various header structures used during communication.

The first bug is the use of 'sizeof' with the pointer of a structure
instead of the structure itself - resulting in the wrong size being
computed.  This is then used in a check to see if the payload
(data_size) would be to large for the preallocated structure.  Since the
bug produces a smaller value for the overhead, it was possible for the
structure to be breached.  (Although the current users of the code do
not currently send enough data to trigger this bug.)

The second bug is that the 'overhead_size' value is used to compute how
much of the preallocated space should be cleared before populating it
with fresh data.  This should have simply been 'sizeof(struct cn_msg)'
not overhead_size.  The fact that 'overhead_size' was computed
incorrectly made this problem "less bad" - leaving only a pointer's
worth of space at the end uncleared.  Thus, this bug was never producing
a bad result, but still needs to be fixed - especially now that the
value is computed correctly.

Cc: stable@kernel.org
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2010-02-16 18:42:53 +00:00

285 lines
7.1 KiB
C

/*
* Copyright (C) 2006-2009 Red Hat, Inc.
*
* This file is released under the LGPL.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <net/sock.h>
#include <linux/workqueue.h>
#include <linux/connector.h>
#include <linux/device-mapper.h>
#include <linux/dm-log-userspace.h>
#include "dm-log-userspace-transfer.h"
static uint32_t dm_ulog_seq;
/*
* Netlink/Connector is an unreliable protocol. How long should
* we wait for a response before assuming it was lost and retrying?
* (If we do receive a response after this time, it will be discarded
* and the response to the resent request will be waited for.
*/
#define DM_ULOG_RETRY_TIMEOUT (15 * HZ)
/*
* Pre-allocated space for speed
*/
#define DM_ULOG_PREALLOCED_SIZE 512
static struct cn_msg *prealloced_cn_msg;
static struct dm_ulog_request *prealloced_ulog_tfr;
static struct cb_id ulog_cn_id = {
.idx = CN_IDX_DM,
.val = CN_VAL_DM_USERSPACE_LOG
};
static DEFINE_MUTEX(dm_ulog_lock);
struct receiving_pkg {
struct list_head list;
struct completion complete;
uint32_t seq;
int error;
size_t *data_size;
char *data;
};
static DEFINE_SPINLOCK(receiving_list_lock);
static struct list_head receiving_list;
static int dm_ulog_sendto_server(struct dm_ulog_request *tfr)
{
int r;
struct cn_msg *msg = prealloced_cn_msg;
memset(msg, 0, sizeof(struct cn_msg));
msg->id.idx = ulog_cn_id.idx;
msg->id.val = ulog_cn_id.val;
msg->ack = 0;
msg->seq = tfr->seq;
msg->len = sizeof(struct dm_ulog_request) + tfr->data_size;
r = cn_netlink_send(msg, 0, gfp_any());
return r;
}
/*
* Parameters for this function can be either msg or tfr, but not
* both. This function fills in the reply for a waiting request.
* If just msg is given, then the reply is simply an ACK from userspace
* that the request was received.
*
* Returns: 0 on success, -ENOENT on failure
*/
static int fill_pkg(struct cn_msg *msg, struct dm_ulog_request *tfr)
{
uint32_t rtn_seq = (msg) ? msg->seq : (tfr) ? tfr->seq : 0;
struct receiving_pkg *pkg;
/*
* The 'receiving_pkg' entries in this list are statically
* allocated on the stack in 'dm_consult_userspace'.
* Each process that is waiting for a reply from the user
* space server will have an entry in this list.
*
* We are safe to do it this way because the stack space
* is unique to each process, but still addressable by
* other processes.
*/
list_for_each_entry(pkg, &receiving_list, list) {
if (rtn_seq != pkg->seq)
continue;
if (msg) {
pkg->error = -msg->ack;
/*
* If we are trying again, we will need to know our
* storage capacity. Otherwise, along with the
* error code, we make explicit that we have no data.
*/
if (pkg->error != -EAGAIN)
*(pkg->data_size) = 0;
} else if (tfr->data_size > *(pkg->data_size)) {
DMERR("Insufficient space to receive package [%u] "
"(%u vs %zu)", tfr->request_type,
tfr->data_size, *(pkg->data_size));
*(pkg->data_size) = 0;
pkg->error = -ENOSPC;
} else {
pkg->error = tfr->error;
memcpy(pkg->data, tfr->data, tfr->data_size);
*(pkg->data_size) = tfr->data_size;
}
complete(&pkg->complete);
return 0;
}
return -ENOENT;
}
/*
* This is the connector callback that delivers data
* that was sent from userspace.
*/
static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
{
struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1);
if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN))
return;
spin_lock(&receiving_list_lock);
if (msg->len == 0)
fill_pkg(msg, NULL);
else if (msg->len < sizeof(*tfr))
DMERR("Incomplete message received (expected %u, got %u): [%u]",
(unsigned)sizeof(*tfr), msg->len, msg->seq);
else
fill_pkg(NULL, tfr);
spin_unlock(&receiving_list_lock);
}
/**
* dm_consult_userspace
* @uuid: log's universal unique identifier (must be DM_UUID_LEN in size)
* @luid: log's local unique identifier
* @request_type: found in include/linux/dm-log-userspace.h
* @data: data to tx to the server
* @data_size: size of data in bytes
* @rdata: place to put return data from server
* @rdata_size: value-result (amount of space given/amount of space used)
*
* rdata_size is undefined on failure.
*
* Memory used to communicate with userspace is zero'ed
* before populating to ensure that no unwanted bits leak
* from kernel space to user-space. All userspace log communications
* between kernel and user space go through this function.
*
* Returns: 0 on success, -EXXX on failure
**/
int dm_consult_userspace(const char *uuid, uint64_t luid, int request_type,
char *data, size_t data_size,
char *rdata, size_t *rdata_size)
{
int r = 0;
size_t dummy = 0;
int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg);
struct dm_ulog_request *tfr = prealloced_ulog_tfr;
struct receiving_pkg pkg;
/*
* Given the space needed to hold the 'struct cn_msg' and
* 'struct dm_ulog_request' - do we have enough payload
* space remaining?
*/
if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) {
DMINFO("Size of tfr exceeds preallocated size");
return -EINVAL;
}
if (!rdata_size)
rdata_size = &dummy;
resend:
/*
* We serialize the sending of requests so we can
* use the preallocated space.
*/
mutex_lock(&dm_ulog_lock);
memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg));
memcpy(tfr->uuid, uuid, DM_UUID_LEN);
tfr->luid = luid;
tfr->seq = dm_ulog_seq++;
/*
* Must be valid request type (all other bits set to
* zero). This reserves other bits for possible future
* use.
*/
tfr->request_type = request_type & DM_ULOG_REQUEST_MASK;
tfr->data_size = data_size;
if (data && data_size)
memcpy(tfr->data, data, data_size);
memset(&pkg, 0, sizeof(pkg));
init_completion(&pkg.complete);
pkg.seq = tfr->seq;
pkg.data_size = rdata_size;
pkg.data = rdata;
spin_lock(&receiving_list_lock);
list_add(&(pkg.list), &receiving_list);
spin_unlock(&receiving_list_lock);
r = dm_ulog_sendto_server(tfr);
mutex_unlock(&dm_ulog_lock);
if (r) {
DMERR("Unable to send log request [%u] to userspace: %d",
request_type, r);
spin_lock(&receiving_list_lock);
list_del_init(&(pkg.list));
spin_unlock(&receiving_list_lock);
goto out;
}
r = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT);
spin_lock(&receiving_list_lock);
list_del_init(&(pkg.list));
spin_unlock(&receiving_list_lock);
if (!r) {
DMWARN("[%s] Request timed out: [%u/%u] - retrying",
(strlen(uuid) > 8) ?
(uuid + (strlen(uuid) - 8)) : (uuid),
request_type, pkg.seq);
goto resend;
}
r = pkg.error;
if (r == -EAGAIN)
goto resend;
out:
return r;
}
int dm_ulog_tfr_init(void)
{
int r;
void *prealloced;
INIT_LIST_HEAD(&receiving_list);
prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL);
if (!prealloced)
return -ENOMEM;
prealloced_cn_msg = prealloced;
prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg);
r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback);
if (r) {
cn_del_callback(&ulog_cn_id);
return r;
}
return 0;
}
void dm_ulog_tfr_exit(void)
{
cn_del_callback(&ulog_cn_id);
kfree(prealloced_cn_msg);
}