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[PATCH] epoll: fix delayed initialization bug 

Al found a potential problem in epoll_create(), where the
file->private_data member was set after fd_install().  This is obviously
wrong since another thread might do a close() on that fd# before we set the
file->private_data member.  This goes over 2.6.13 and passes a few basic
tests I've done here.

(akpm: snuck in a kzalloc() cleanup too)

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Davide Libenzi 2005-09-16 19:28:06 -07:00 committed by Linus Torvalds
parent dda8577fb5
commit 53d2be79d5
1 changed files with 20 additions and 20 deletions
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40
fs/eventpoll.c
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@ -231,8 +231,9 @@ struct ep_pqueue {
static void ep_poll_safewake_init(struct poll_safewake *psw);
static void ep_poll_safewake(struct poll_safewake *psw, wait_queue_head_t *wq);
static int ep_getfd(int *efd, struct inode **einode, struct file **efile);
static int ep_file_init(struct file *file);
static int ep_getfd(int *efd, struct inode **einode, struct file **efile,
struct eventpoll *ep);
static int ep_alloc(struct eventpoll **pep);
static void ep_free(struct eventpoll *ep);
static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd);
static void ep_use_epitem(struct epitem *epi);
@ -501,38 +502,37 @@ void eventpoll_release_file(struct file *file)
asmlinkage long sys_epoll_create(int size)
{
int error, fd;
struct eventpoll *ep;
struct inode *inode;
struct file *file;
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d)\n",
current, size));
/* Sanity check on the size parameter */
/*
* Sanity check on the size parameter, and create the internal data
* structure ( "struct eventpoll" ).
*/
error = -EINVAL;
if (size <= 0)
if (size <= 0 || (error = ep_alloc(&ep)) != 0)
goto eexit_1;
/*
* Creates all the items needed to setup an eventpoll file. That is,
* a file structure, and inode and a free file descriptor.
*/
error = ep_getfd(&fd, &inode, &file);
if (error)
goto eexit_1;
/* Setup the file internal data structure ( "struct eventpoll" ) */
error = ep_file_init(file);
error = ep_getfd(&fd, &inode, &file, ep);
if (error)
goto eexit_2;
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
current, size, fd));
return fd;
eexit_2:
sys_close(fd);
ep_free(ep);
kfree(ep);
eexit_1:
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_create(%d) = %d\n",
current, size, error));
@ -706,7 +706,8 @@ eexit_1:
/*
* Creates the file descriptor to be used by the epoll interface.
*/
static int ep_getfd(int *efd, struct inode **einode, struct file **efile)
static int ep_getfd(int *efd, struct inode **einode, struct file **efile,
struct eventpoll *ep)
{
struct qstr this;
char name[32];
@ -756,7 +757,7 @@ static int ep_getfd(int *efd, struct inode **einode, struct file **efile)
file->f_op = &eventpoll_fops;
file->f_mode = FMODE_READ;
file->f_version = 0;
file->private_data = NULL;
file->private_data = ep;
/* Install the new setup file into the allocated fd. */
fd_install(fd, file);
@ -777,14 +778,13 @@ eexit_1:
}
static int ep_file_init(struct file *file)
static int ep_alloc(struct eventpoll **pep)
{
struct eventpoll *ep;
struct eventpoll *ep = kzalloc(sizeof(*ep), GFP_KERNEL);
if (!(ep = kmalloc(sizeof(struct eventpoll), GFP_KERNEL)))
if (!ep)
return -ENOMEM;
memset(ep, 0, sizeof(*ep));
rwlock_init(&ep->lock);
init_rwsem(&ep->sem);
init_waitqueue_head(&ep->wq);
@ -792,9 +792,9 @@ static int ep_file_init(struct file *file)
INIT_LIST_HEAD(&ep->rdllist);
ep->rbr = RB_ROOT;
file->private_data = ep;
*pep = ep;
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_file_init() ep=%p\n",
DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_alloc() ep=%p\n",
current, ep));
return 0;
}