Skip to content

Commit

Permalink
SUNRPC: Fix a potential race in rpc_wake_up_task()
Browse files Browse the repository at this point in the history 
Use RCU to ensure that we can safely call rpc_finish_wakeup after we've
called __rpc_do_wake_up_task. If not, there is a theoretical race, in which
the rpc_task finishes executing, and gets freed first.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
  • Loading branch information
Trond Myklebust authored and Trond Myklebust committed Dec 6, 2006
1 parent e6b3c4d commit 8aca67f
Show file tree
Hide file tree
Showing 5 changed files with 47 additions and 20 deletions.
8 changes: 7 additions & 1 deletion fs/nfs/read.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -65,13 +65,19 @@ struct nfs_read_data *nfs_readdata_alloc(size_t len)
return p;
}

static void nfs_readdata_free(struct nfs_read_data *p)
static void nfs_readdata_rcu_free(struct rcu_head *head)
{
struct nfs_read_data *p = container_of(head, struct nfs_read_data, task.u.tk_rcu);
if (p && (p->pagevec != &p->page_array[0]))
kfree(p->pagevec);
mempool_free(p, nfs_rdata_mempool);
}

static void nfs_readdata_free(struct nfs_read_data *rdata)
{
call_rcu_bh(&rdata->task.u.tk_rcu, nfs_readdata_rcu_free);
}

void nfs_readdata_release(void *data)
{
nfs_readdata_free(data);
Expand Down
20 changes: 16 additions & 4 deletions fs/nfs/write.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -102,13 +102,19 @@ struct nfs_write_data *nfs_commit_alloc(void)
return p;
}

void nfs_commit_free(struct nfs_write_data *p)
void nfs_commit_rcu_free(struct rcu_head *head)
{
struct nfs_write_data *p = container_of(head, struct nfs_write_data, task.u.tk_rcu);
if (p && (p->pagevec != &p->page_array[0]))
kfree(p->pagevec);
mempool_free(p, nfs_commit_mempool);
}

void nfs_commit_free(struct nfs_write_data *wdata)
{
call_rcu_bh(&wdata->task.u.tk_rcu, nfs_commit_rcu_free);
}

struct nfs_write_data *nfs_writedata_alloc(size_t len)
{
unsigned int pagecount = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
Expand All @@ -131,13 +137,19 @@ struct nfs_write_data *nfs_writedata_alloc(size_t len)
return p;
}

static void nfs_writedata_free(struct nfs_write_data *p)
static void nfs_writedata_rcu_free(struct rcu_head *head)
{
struct nfs_write_data *p = container_of(head, struct nfs_write_data, task.u.tk_rcu);
if (p && (p->pagevec != &p->page_array[0]))
kfree(p->pagevec);
mempool_free(p, nfs_wdata_mempool);
}

static void nfs_writedata_free(struct nfs_write_data *wdata)
{
call_rcu_bh(&wdata->task.u.tk_rcu, nfs_writedata_rcu_free);
}

void nfs_writedata_release(void *wdata)
{
nfs_writedata_free(wdata);
Expand Down Expand Up @@ -258,7 +270,7 @@ static int nfs_writepage_sync(struct nfs_open_context *ctx, struct inode *inode,
io_error:
nfs_end_data_update(inode);
end_page_writeback(page);
nfs_writedata_free(wdata);
nfs_writedata_release(wdata);
return written ? written : result;
}

Expand Down Expand Up @@ -1043,7 +1055,7 @@ static int nfs_flush_multi(struct inode *inode, struct list_head *head, int how)
while (!list_empty(&list)) {
data = list_entry(list.next, struct nfs_write_data, pages);
list_del(&data->pages);
nfs_writedata_free(data);
nfs_writedata_release(data);
}
nfs_mark_request_dirty(req);
nfs_clear_page_writeback(req);
Expand Down
7 changes: 2 additions & 5 deletions include/linux/nfs_fs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -428,18 +428,15 @@ extern int nfs_updatepage(struct file *, struct page *, unsigned int, unsigned
extern int nfs_writeback_done(struct rpc_task *, struct nfs_write_data *);
extern void nfs_writedata_release(void *);

#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
struct nfs_write_data *nfs_commit_alloc(void);
void nfs_commit_free(struct nfs_write_data *p);
#endif

/*
* Try to write back everything synchronously (but check the
* return value!)
*/
extern int nfs_sync_inode_wait(struct inode *, unsigned long, unsigned int, int);
#if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
extern int nfs_commit_inode(struct inode *, int);
extern struct nfs_write_data *nfs_commit_alloc(void);
extern void nfs_commit_free(struct nfs_write_data *wdata);
extern void nfs_commit_release(void *wdata);
#else
static inline int
Expand Down
2 changes: 2 additions & 0 deletions include/linux/sunrpc/sched.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@

#include <linux/timer.h>
#include <linux/sunrpc/types.h>
#include <linux/rcupdate.h>
#include <linux/spinlock.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
Expand Down Expand Up @@ -85,6 +86,7 @@ struct rpc_task {
union {
struct work_struct tk_work; /* Async task work queue */
struct rpc_wait tk_wait; /* RPC wait */
struct rcu_head tk_rcu; /* for task deletion */
} u;

unsigned short tk_timeouts; /* maj timeouts */
Expand Down
30 changes: 20 additions & 10 deletions net/sunrpc/sched.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -427,16 +427,19 @@ __rpc_default_timer(struct rpc_task *task)
*/
void rpc_wake_up_task(struct rpc_task *task)
{
rcu_read_lock_bh();
if (rpc_start_wakeup(task)) {
if (RPC_IS_QUEUED(task)) {
struct rpc_wait_queue *queue = task->u.tk_wait.rpc_waitq;

spin_lock_bh(&queue->lock);
/* Note: we're already in a bh-safe context */
spin_lock(&queue->lock);
__rpc_do_wake_up_task(task);
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
}
rpc_finish_wakeup(task);
}
rcu_read_unlock_bh();
}

/*
Expand Down Expand Up @@ -499,14 +502,16 @@ struct rpc_task * rpc_wake_up_next(struct rpc_wait_queue *queue)
struct rpc_task *task = NULL;

dprintk("RPC: wake_up_next(%p \"%s\")\n", queue, rpc_qname(queue));
spin_lock_bh(&queue->lock);
rcu_read_lock_bh();
spin_lock(&queue->lock);
if (RPC_IS_PRIORITY(queue))
task = __rpc_wake_up_next_priority(queue);
else {
task_for_first(task, &queue->tasks[0])
__rpc_wake_up_task(task);
}
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
rcu_read_unlock_bh();

return task;
}
Expand All @@ -522,7 +527,8 @@ void rpc_wake_up(struct rpc_wait_queue *queue)
struct rpc_task *task, *next;
struct list_head *head;

spin_lock_bh(&queue->lock);
rcu_read_lock_bh();
spin_lock(&queue->lock);
head = &queue->tasks[queue->maxpriority];
for (;;) {
list_for_each_entry_safe(task, next, head, u.tk_wait.list)
Expand All @@ -531,7 +537,8 @@ void rpc_wake_up(struct rpc_wait_queue *queue)
break;
head--;
}
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
rcu_read_unlock_bh();
}

/**
Expand All @@ -546,7 +553,8 @@ void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
struct rpc_task *task, *next;
struct list_head *head;

spin_lock_bh(&queue->lock);
rcu_read_lock_bh();
spin_lock(&queue->lock);
head = &queue->tasks[queue->maxpriority];
for (;;) {
list_for_each_entry_safe(task, next, head, u.tk_wait.list) {
Expand All @@ -557,7 +565,8 @@ void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
break;
head--;
}
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
rcu_read_unlock_bh();
}

static void __rpc_atrun(struct rpc_task *task)
Expand Down Expand Up @@ -817,8 +826,9 @@ rpc_alloc_task(void)
return (struct rpc_task *)mempool_alloc(rpc_task_mempool, GFP_NOFS);
}

static void rpc_free_task(struct rpc_task *task)
static void rpc_free_task(struct rcu_head *rcu)
{
struct rpc_task *task = container_of(rcu, struct rpc_task, u.tk_rcu);
dprintk("RPC: %4d freeing task\n", task->tk_pid);
mempool_free(task, rpc_task_mempool);
}
Expand Down Expand Up @@ -872,7 +882,7 @@ void rpc_put_task(struct rpc_task *task)
task->tk_client = NULL;
}
if (task->tk_flags & RPC_TASK_DYNAMIC)
rpc_free_task(task);
call_rcu_bh(&task->u.tk_rcu, rpc_free_task);
if (tk_ops->rpc_release)
tk_ops->rpc_release(calldata);
}
Expand Down

0 comments on commit 8aca67f

Please sign in to comment.