[ Upstream commit 728356dedeff8ef999cb436c71333ef4ac51a81c ]
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@codewrec... Co-developed-by: Dominique Martinet dominique.martinet@cea.fr Signed-off-by: Tomas Bortoli tomasbortoli@gmail.com Reported-by: syzbot+467050c1ce275af2a5b8@syzkaller.appspotmail.com Signed-off-by: Dominique Martinet dominique.martinet@cea.fr Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/9p/client.h | 14 ++++++++++ net/9p/client.c | 57 ++++++++++++++++++++++++++++++++++++----- net/9p/trans_fd.c | 11 +++++++- net/9p/trans_rdma.c | 1 + net/9p/trans_virtio.c | 26 ++++++++++++++++--- net/9p/trans_xen.c | 1 + 6 files changed, 98 insertions(+), 12 deletions(-)
diff --git a/include/net/9p/client.h b/include/net/9p/client.h index 735f3979d559..947a570307a6 100644 --- a/include/net/9p/client.h +++ b/include/net/9p/client.h @@ -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); diff --git a/net/9p/client.c b/net/9p/client.c index 3cde9f619980..4becde979462 100644 --- a/net/9p/client.c +++ b/net/9p/client.c @@ -313,6 +313,18 @@ 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: @@ -336,10 +348,21 @@ 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; @@ -353,7 +376,7 @@ 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; @@ -362,11 +385,23 @@ 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 @@ -382,7 +417,9 @@ 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(); } @@ -406,6 +443,7 @@ 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);
@@ -646,9 +684,10 @@ 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; @@ -685,6 +724,8 @@ 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); }
@@ -719,6 +760,8 @@ 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; @@ -2259,7 +2302,7 @@ 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; }
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index 51615c0fb744..aca528722183 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -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; } diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c index 5b0cda1aaa7a..9cc9b3a19ee7 100644 --- a/net/9p/trans_rdma.c +++ b/net/9p/trans_rdma.c @@ -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); }
diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c index 3dd6ce1c0f2d..eb596c2ed546 100644 --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.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 diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c index 782a07f2ad0c..e2fbf3677b9b 100644 --- a/net/9p/trans_xen.c +++ b/net/9p/trans_xen.c @@ -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; }