github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-07-27 17:47:41 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

xprtrdma: Fix ep kref imbalance on ADDR_CHANGE

Browse Source 
rpcrdma_cm_event_handler() falls through to the disconnected: label
on RDMA_CM_EVENT_ADDR_CHANGE and calls rpcrdma_ep_put() with no
matching get when the event arrives before RDMA_CM_EVENT_ESTABLISHED.
The kref then underflows during connect teardown and
rpcrdma_xprt_disconnect() operates on a freed ep.

Reference counts across a normal connection lifecycle:

    rpcrdma_ep_create()             kref_init     ->1
    rpcrdma_xprt_connect()          ep_get        ->2  (before post_recvs)
    RDMA_CM_EVENT_ESTABLISHED       ep_get        ->3
    RDMA_CM_EVENT_DISCONNECTED      ep_put        ->2
    rpcrdma_xprt_drain()            ep_put        ->1
    rpcrdma_xprt_disconnect() tail  ep_put        ->0  (ep_destroy)

The connect-time get in rpcrdma_xprt_connect(), taken just before
rpcrdma_post_recvs() "while there are outstanding Receives," is
balanced by rpcrdma_xprt_drain. ADDR_CHANGE before ESTABLISHED has
no get to consume, so its put drops the count to 1 and the drain
put then frees the ep while rpcrdma_xprt_disconnect() still holds a
pointer to it.

Fix by dispatching on the prior re_connect_status via xchg(): for
prev == 0 (pre-ESTABLISHED) wake the connect waiter and return with
no put; for prev == 1 call rpcrdma_force_disconnect() and return.
The case-1 arm relies on the subsequent RDMA_CM_EVENT_DISCONNECTED
event -- reliably delivered when rdma_disconnect() is called on a
still-connected cm_id -- to balance the ESTABLISHED get;
rpcrdma_xprt_drain() continues to balance only that connect-time
get. Any other prior value means teardown is already in flight.

Fixes: 2acc5cae29 ("xprtrdma: Prevent dereferencing r_xprt->rx_ep after it is freed")
Assisted-by: kres:claude-opus-4-7
Signed-off-by: Chris Mason <clm@meta.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <anna.schumaker@hammerspace.com>
This commit is contained in:
Chris Mason 2026-06-04 13:06:33 -04:00 committed by Anna Schumaker
parent 417efc5202
commit af9b65b29a
1 changed files with 11 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
net/sunrpc/xprtrdma/verbs.c
View File

@ -245,8 +245,17 @@ rpcrdma_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event)
complete(&ep->re_done);
return 0;
case RDMA_CM_EVENT_ADDR_CHANGE:
ep->re_connect_status = -ENODEV;
goto disconnected;
switch (xchg(&ep->re_connect_status, -ENODEV)) {
case 0:
goto wake_connect_worker;
case 1:
/* The later DISCONNECTED event balances the
* ESTABLISHED get; do not put here.
*/
rpcrdma_force_disconnect(ep);
return 0;
}
return 0;
case RDMA_CM_EVENT_ESTABLISHED:
rpcrdma_ep_get(ep);
ep->re_connect_status = 1;
@ -269,7 +278,6 @@ rpcrdma_cm_event_handler(struct rdma_cm_id *id, struct rdma_cm_event *event)
return 0;
case RDMA_CM_EVENT_DISCONNECTED:
ep->re_connect_status = -ECONNABORTED;
disconnected:
rpcrdma_force_disconnect(ep);
return rpcrdma_ep_put(ep);
default: