Commit 728356de authored by Tomas Bortoli's avatar Tomas Bortoli Committed by Dominique Martinet

9p: Add refcount to p9_req_t

To avoid use-after-free(s), use a refcount to keep track of the
usable references to any instantiated struct p9_req_t.

This commit adds p9_req_put(), p9_req_get() and p9_req_try_get() as
wrappers to kref_put(), kref_get() and kref_get_unless_zero().
These are used by the client and the transports to keep track of
valid requests' references.

p9_free_req() is added back and used as callback by kref_put().

Add SLAB_TYPESAFE_BY_RCU as it ensures that the memory freed by
kmem_cache_free() will not be reused for another type until the rcu
synchronisation period is over, so an address gotten under rcu read
lock is safe to inc_ref() without corrupting random memory while
the lock is held.

Link: http://lkml.kernel.org/r/1535626341-20693-1-git-send-email-asmadeus@codewreck.orgCo-developed-by: default avatarDominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: default avatarTomas Bortoli <tomasbortoli@gmail.com>
Reported-by: syzbot+467050c1ce275af2a5b8@syzkaller.appspotmail.com
Signed-off-by: default avatarDominique Martinet <dominique.martinet@cea.fr>
parent 43cbcbee
......@@ -94,6 +94,7 @@ enum p9_req_status_t {
struct p9_req_t {
int status;
int t_err;
struct kref refcount;
wait_queue_head_t wq;
struct p9_fcall tc;
struct p9_fcall rc;
......@@ -233,6 +234,19 @@ int p9_client_lock_dotl(struct p9_fid *fid, struct p9_flock *flock, u8 *status);
int p9_client_getlock_dotl(struct p9_fid *fid, struct p9_getlock *fl);
void p9_fcall_fini(struct p9_fcall *fc);
struct p9_req_t *p9_tag_lookup(struct p9_client *, u16);
static inline void p9_req_get(struct p9_req_t *r)
{
kref_get(&r->refcount);
}
static inline int p9_req_try_get(struct p9_req_t *r)
{
return kref_get_unless_zero(&r->refcount);
}
int p9_req_put(struct p9_req_t *r);
void p9_client_cb(struct p9_client *c, struct p9_req_t *req, int status);
int p9_parse_header(struct p9_fcall *, int32_t *, int8_t *, int16_t *, int);
......
......@@ -307,6 +307,18 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size)
if (tag < 0)
goto free;
/* Init ref to two because in the general case there is one ref
* that is put asynchronously by a writer thread, one ref
* temporarily given by p9_tag_lookup and put by p9_client_cb
* in the recv thread, and one ref put by p9_tag_remove in the
* main thread. The only exception is virtio that does not use
* p9_tag_lookup but does not have a writer thread either
* (the write happens synchronously in the request/zc_request
* callback), so p9_client_cb eats the second ref there
* as the pointer is duplicated directly by virtqueue_add_sgs()
*/
refcount_set(&req->refcount.refcount, 2);
return req;
free:
......@@ -330,10 +342,21 @@ struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16 tag)
struct p9_req_t *req;
rcu_read_lock();
again:
req = idr_find(&c->reqs, tag);
/* There's no refcount on the req; a malicious server could cause
* us to dereference a NULL pointer
*/
if (req) {
/* We have to be careful with the req found under rcu_read_lock
* Thanks to SLAB_TYPESAFE_BY_RCU we can safely try to get the
* ref again without corrupting other data, then check again
* that the tag matches once we have the ref
*/
if (!p9_req_try_get(req))
goto again;
if (req->tc.tag != tag) {
p9_req_put(req);
goto again;
}
}
rcu_read_unlock();
return req;
......@@ -347,7 +370,7 @@ EXPORT_SYMBOL(p9_tag_lookup);
*
* Context: Any context.
*/
static void p9_tag_remove(struct p9_client *c, struct p9_req_t *r)
static int p9_tag_remove(struct p9_client *c, struct p9_req_t *r)
{
unsigned long flags;
u16 tag = r->tc.tag;
......@@ -356,11 +379,23 @@ static void p9_tag_remove(struct p9_client *c, struct p9_req_t *r)
spin_lock_irqsave(&c->lock, flags);
idr_remove(&c->reqs, tag);
spin_unlock_irqrestore(&c->lock, flags);
return p9_req_put(r);
}
static void p9_req_free(struct kref *ref)
{
struct p9_req_t *r = container_of(ref, struct p9_req_t, refcount);
p9_fcall_fini(&r->tc);
p9_fcall_fini(&r->rc);
kmem_cache_free(p9_req_cache, r);
}
int p9_req_put(struct p9_req_t *r)
{
return kref_put(&r->refcount, p9_req_free);
}
EXPORT_SYMBOL(p9_req_put);
/**
* p9_tag_cleanup - cleans up tags structure and reclaims resources
* @c: v9fs client struct
......@@ -376,7 +411,9 @@ static void p9_tag_cleanup(struct p9_client *c)
rcu_read_lock();
idr_for_each_entry(&c->reqs, req, id) {
pr_info("Tag %d still in use\n", id);
p9_tag_remove(c, req);
if (p9_tag_remove(c, req) == 0)
pr_warn("Packet with tag %d has still references",
req->tc.tag);
}
rcu_read_unlock();
}
......@@ -400,6 +437,7 @@ void p9_client_cb(struct p9_client *c, struct p9_req_t *req, int status)
wake_up(&req->wq);
p9_debug(P9_DEBUG_MUX, "wakeup: %d\n", req->tc.tag);
p9_req_put(req);
}
EXPORT_SYMBOL(p9_client_cb);
......@@ -640,9 +678,10 @@ static int p9_client_flush(struct p9_client *c, struct p9_req_t *oldreq)
* if we haven't received a response for oldreq,
* remove it from the list
*/
if (oldreq->status == REQ_STATUS_SENT)
if (oldreq->status == REQ_STATUS_SENT) {
if (c->trans_mod->cancelled)
c->trans_mod->cancelled(c, oldreq);
}
p9_tag_remove(c, req);
return 0;
......@@ -679,6 +718,8 @@ static struct p9_req_t *p9_client_prepare_req(struct p9_client *c,
return req;
reterr:
p9_tag_remove(c, req);
/* We have to put also the 2nd reference as it won't be used */
p9_req_put(req);
return ERR_PTR(err);
}
......@@ -713,6 +754,8 @@ p9_client_rpc(struct p9_client *c, int8_t type, const char *fmt, ...)
err = c->trans_mod->request(c, req);
if (err < 0) {
/* write won't happen */
p9_req_put(req);
if (err != -ERESTARTSYS && err != -EFAULT)
c->status = Disconnected;
goto recalc_sigpending;
......@@ -2238,7 +2281,7 @@ EXPORT_SYMBOL(p9_client_readlink);
int __init p9_client_init(void)
{
p9_req_cache = KMEM_CACHE(p9_req_t, 0);
p9_req_cache = KMEM_CACHE(p9_req_t, SLAB_TYPESAFE_BY_RCU);
return p9_req_cache ? 0 : -ENOMEM;
}
......
......@@ -132,6 +132,7 @@ struct p9_conn {
struct list_head req_list;
struct list_head unsent_req_list;
struct p9_req_t *req;
struct p9_req_t *wreq;
char tmp_buf[7];
struct p9_fcall rc;
int wpos;
......@@ -383,6 +384,7 @@ static void p9_read_work(struct work_struct *work)
m->rc.sdata = NULL;
m->rc.offset = 0;
m->rc.capacity = 0;
p9_req_put(m->req);
m->req = NULL;
}
......@@ -472,6 +474,8 @@ static void p9_write_work(struct work_struct *work)
m->wbuf = req->tc.sdata;
m->wsize = req->tc.size;
m->wpos = 0;
p9_req_get(req);
m->wreq = req;
spin_unlock(&m->client->lock);
}
......@@ -492,8 +496,11 @@ static void p9_write_work(struct work_struct *work)
}
m->wpos += err;
if (m->wpos == m->wsize)
if (m->wpos == m->wsize) {
m->wpos = m->wsize = 0;
p9_req_put(m->wreq);
m->wreq = NULL;
}
end_clear:
clear_bit(Wworksched, &m->wsched);
......@@ -694,6 +701,7 @@ static int p9_fd_cancel(struct p9_client *client, struct p9_req_t *req)
if (req->status == REQ_STATUS_UNSENT) {
list_del(&req->req_list);
req->status = REQ_STATUS_FLSHD;
p9_req_put(req);
ret = 0;
}
spin_unlock(&client->lock);
......@@ -711,6 +719,7 @@ static int p9_fd_cancelled(struct p9_client *client, struct p9_req_t *req)
spin_lock(&client->lock);
list_del(&req->req_list);
spin_unlock(&client->lock);
p9_req_put(req);
return 0;
}
......
......@@ -365,6 +365,7 @@ send_done(struct ib_cq *cq, struct ib_wc *wc)
c->busa, c->req->tc.size,
DMA_TO_DEVICE);
up(&rdma->sq_sem);
p9_req_put(c->req);
kfree(c);
}
......
......@@ -207,6 +207,13 @@ static int p9_virtio_cancel(struct p9_client *client, struct p9_req_t *req)
return 1;
}
/* Reply won't come, so drop req ref */
static int p9_virtio_cancelled(struct p9_client *client, struct p9_req_t *req)
{
p9_req_put(req);
return 0;
}
/**
* pack_sg_list_p - Just like pack_sg_list. Instead of taking a buffer,
* this takes a list of pages.
......@@ -404,6 +411,7 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
struct scatterlist *sgs[4];
size_t offs;
int need_drop = 0;
int kicked = 0;
p9_debug(P9_DEBUG_TRANS, "virtio request\n");
......@@ -411,8 +419,10 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
__le32 sz;
int n = p9_get_mapped_pages(chan, &out_pages, uodata,
outlen, &offs, &need_drop);
if (n < 0)
return n;
if (n < 0) {
err = n;
goto err_out;
}
out_nr_pages = DIV_ROUND_UP(n + offs, PAGE_SIZE);
if (n != outlen) {
__le32 v = cpu_to_le32(n);
......@@ -428,8 +438,10 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
} else if (uidata) {
int n = p9_get_mapped_pages(chan, &in_pages, uidata,
inlen, &offs, &need_drop);
if (n < 0)
return n;
if (n < 0) {
err = n;
goto err_out;
}
in_nr_pages = DIV_ROUND_UP(n + offs, PAGE_SIZE);
if (n != inlen) {
__le32 v = cpu_to_le32(n);
......@@ -498,6 +510,7 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
}
virtqueue_kick(chan->vq);
spin_unlock_irqrestore(&chan->lock, flags);
kicked = 1;
p9_debug(P9_DEBUG_TRANS, "virtio request kicked\n");
err = wait_event_killable(req->wq, req->status >= REQ_STATUS_RCVD);
/*
......@@ -518,6 +531,10 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
}
kvfree(in_pages);
kvfree(out_pages);
if (!kicked) {
/* reply won't come */
p9_req_put(req);
}
return err;
}
......@@ -750,6 +767,7 @@ static struct p9_trans_module p9_virtio_trans = {
.request = p9_virtio_request,
.zc_request = p9_virtio_zc_request,
.cancel = p9_virtio_cancel,
.cancelled = p9_virtio_cancelled,
/*
* We leave one entry for input and one entry for response
* headers. We also skip one more entry to accomodate, address
......
......@@ -185,6 +185,7 @@ static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
ring->intf->out_prod = prod;
spin_unlock_irqrestore(&ring->lock, flags);
notify_remote_via_irq(ring->irq);
p9_req_put(p9_req);
return 0;
}
......
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