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SUNRPC: Fix a race between work-queue and rpc_killall_tasks 

Since rpc_killall_tasks may modify the rpc_task's tk_action field
without any locking, we need to be careful when dereferencing it.

Reported-by: Ben Greear <greearb@candelatech.com>
Tested-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org
This commit is contained in:
Trond Myklebust 2011-07-06 19:58:23 -04:00
parent 2bea038c52
commit b55c59892e
1 changed files with 11 additions and 16 deletions
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27
net/sunrpc/sched.c
View File

@ -616,30 +616,25 @@ static void __rpc_execute(struct rpc_task *task)
BUG_ON(RPC_IS_QUEUED(task));
for (;;) {
void (*do_action)(struct rpc_task *);
/*
* Execute any pending callback.
* Execute any pending callback first.
*/
if (task->tk_callback) {
void (*save_callback)(struct rpc_task *);
/*
* We set tk_callback to NULL before calling it,
* in case it sets the tk_callback field itself:
*/
save_callback = task->tk_callback;
task->tk_callback = NULL;
save_callback(task);
} else {
do_action = task->tk_callback;
task->tk_callback = NULL;
if (do_action == NULL) {
/*
* Perform the next FSM step.
* tk_action may be NULL when the task has been killed
* by someone else.
* tk_action may be NULL if the task has been killed.
* In particular, note that rpc_killall_tasks may
* do this at any time, so beware when dereferencing.
*/
if (task->tk_action == NULL)
do_action = task->tk_action;
if (do_action == NULL)
break;
task->tk_action(task);
}
do_action(task);
/*
* Lockless check for whether task is sleeping or not.