* [PATCH] IB/sa: Resolving use-after-free in ib_nl_send_msg.
2020-05-14 15:11 Review Request Divya Indi
@ 2020-05-14 15:11 ` Divya Indi
2020-05-26 0:31 ` Jason Gunthorpe
0 siblings, 1 reply; 3+ messages in thread
From: Divya Indi @ 2020-05-14 15:11 UTC (permalink / raw)
To: linux-kernel, linux-rdma, Jason Gunthorpe, Kaike Wan
Cc: Gerd Rausch, Håkon Bugge, Srinivas Eeda, Rama Nichanamatlu,
Doug Ledford, Divya Indi
This patch fixes commit -
commit 3ebd2fd0d011 ("IB/sa: Put netlink request into the request list before sending")'
Above commit adds the query to the request list before ib_nl_snd_msg.
However, if there is a delay in sending out the request (For
eg: Delay due to low memory situation) the timer to handle request timeout
might kick in before the request is sent out to ibacm via netlink.
ib_nl_request_timeout may release the query if it fails to send it to SA
as well causing a use after free situation.
Call Trace for the above race:
[<ffffffffa02f43cb>] ? ib_pack+0x17b/0x240 [ib_core]
[<ffffffffa032aef1>] ib_sa_path_rec_get+0x181/0x200 [ib_sa]
[<ffffffffa0379db0>] rdma_resolve_route+0x3c0/0x8d0 [rdma_cm]
[<ffffffffa0374450>] ? cma_bind_port+0xa0/0xa0 [rdma_cm]
[<ffffffffa040f850>] ? rds_rdma_cm_event_handler_cmn+0x850/0x850
[rds_rdma]
[<ffffffffa040f22c>] rds_rdma_cm_event_handler_cmn+0x22c/0x850
[rds_rdma]
[<ffffffffa040f860>] rds_rdma_cm_event_handler+0x10/0x20 [rds_rdma]
[<ffffffffa037778e>] addr_handler+0x9e/0x140 [rdma_cm]
[<ffffffffa026cdb4>] process_req+0x134/0x190 [ib_addr]
[<ffffffff810a02f9>] process_one_work+0x169/0x4a0
[<ffffffff810a0b2b>] worker_thread+0x5b/0x560
[<ffffffff810a0ad0>] ? flush_delayed_work+0x50/0x50
[<ffffffff810a68fb>] kthread+0xcb/0xf0
[<ffffffff816ec49a>] ? __schedule+0x24a/0x810
[<ffffffff816ec49a>] ? __schedule+0x24a/0x810
[<ffffffff810a6830>] ? kthread_create_on_node+0x180/0x180
[<ffffffff816f25a7>] ret_from_fork+0x47/0x90
[<ffffffff810a6830>] ? kthread_create_on_node+0x180/0x180
....
RIP [<ffffffffa03296cd>] send_mad+0x33d/0x5d0 [ib_sa]
To resolve this issue, we introduce a new flag IB_SA_NL_QUERY_SENT.
This flag Indicates if the request has been sent out to ibacm yet.
If this flag is not set for a query and the query times out, we add it
back to the list with the original delay.
To handle the case where a response is received before we could set this
flag, the response handler waits for the flag to be
set before proceeding with the query.
Signed-off-by: Divya Indi <divya.indi@oracle.com>
---
drivers/infiniband/core/sa_query.c | 53 ++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
diff --git a/drivers/infiniband/core/sa_query.c b/drivers/infiniband/core/sa_query.c
index 30d4c12..91486e7 100644
--- a/drivers/infiniband/core/sa_query.c
+++ b/drivers/infiniband/core/sa_query.c
@@ -42,6 +42,7 @@
#include <linux/kref.h>
#include <linux/xarray.h>
#include <linux/workqueue.h>
+#include <linux/bitops.h>
#include <uapi/linux/if_ether.h>
#include <rdma/ib_pack.h>
#include <rdma/ib_cache.h>
@@ -59,6 +60,9 @@
#define IB_SA_LOCAL_SVC_TIMEOUT_MAX 200000
#define IB_SA_CPI_MAX_RETRY_CNT 3
#define IB_SA_CPI_RETRY_WAIT 1000 /*msecs */
+
+DECLARE_WAIT_QUEUE_HEAD(wait_queue);
+
static int sa_local_svc_timeout_ms = IB_SA_LOCAL_SVC_TIMEOUT_DEFAULT;
struct ib_sa_sm_ah {
@@ -123,6 +127,12 @@ struct ib_sa_query {
#define IB_SA_CANCEL 0x00000002
#define IB_SA_QUERY_OPA 0x00000004
+/*
+ * This bit in the SA query flags indicates whether the query
+ * has been sent out to ibacm via netlink
+ */
+#define IB_SA_NL_QUERY_SENT 3
+
struct ib_sa_service_query {
void (*callback)(int, struct ib_sa_service_rec *, void *);
void *context;
@@ -746,6 +756,11 @@ static inline int ib_sa_query_cancelled(struct ib_sa_query *query)
return (query->flags & IB_SA_CANCEL);
}
+static inline int ib_sa_nl_query_sent(struct ib_sa_query *query)
+{
+ return test_bit(IB_SA_NL_QUERY_SENT, (unsigned long *)&query->flags);
+}
+
static void ib_nl_set_path_rec_attrs(struct sk_buff *skb,
struct ib_sa_query *query)
{
@@ -889,6 +904,15 @@ static int ib_nl_make_request(struct ib_sa_query *query, gfp_t gfp_mask)
spin_lock_irqsave(&ib_nl_request_lock, flags);
list_del(&query->list);
spin_unlock_irqrestore(&ib_nl_request_lock, flags);
+ } else {
+ set_bit(IB_SA_NL_QUERY_SENT, (unsigned long *)&query->flags);
+
+ /*
+ * If response is received before this flag was set
+ * someone is waiting to process the response and release the
+ * query.
+ */
+ wake_up(&wait_queue);
}
return ret;
@@ -994,6 +1018,21 @@ static void ib_nl_request_timeout(struct work_struct *work)
}
list_del(&query->list);
+
+ /*
+ * If IB_SA_NL_QUERY_SENT is not set, this query has not been
+ * sent to ibacm yet. Reset the timer.
+ */
+ if (!ib_sa_nl_query_sent(query)) {
+ delay = msecs_to_jiffies(sa_local_svc_timeout_ms);
+ query->timeout = delay + jiffies;
+ list_add_tail(&query->list, &ib_nl_request_list);
+ /* Start the timeout if this is the only request */
+ if (ib_nl_request_list.next == &query->list)
+ queue_delayed_work(ib_nl_wq, &ib_nl_timed_work,
+ delay);
+ break;
+ }
ib_sa_disable_local_svc(query);
/* Hold the lock to protect against query cancellation */
if (ib_sa_query_cancelled(query))
@@ -1122,6 +1161,20 @@ int ib_nl_handle_resolve_resp(struct sk_buff *skb,
}
send_buf = query->mad_buf;
+ /*
+ * In case of a quick response ie when a response comes in before
+ * setting IB_SA_NL_QUERY_SENT, we can have an unlikely race where the
+ * response handler will release the query, but we can still access the
+ * freed query while setting the flag.
+ * Hence, before proceeding and eventually releasing the query -
+ * wait till the flag is set. The flag should be set soon since getting
+ * a response is indicative of having successfully sent the query.
+ */
+ if (unlikely(!ib_sa_nl_query_sent(query))) {
+ spin_unlock_irqrestore(&ib_nl_request_lock, flags);
+ wait_event(wait_queue, ib_sa_nl_query_sent(query));
+ spin_lock_irqsave(&ib_nl_request_lock, flags);
+ }
if (!ib_nl_is_good_resolve_resp(nlh)) {
/* if the result is a failure, send out the packet via IB */
--
1.8.3.1
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