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inotify: fix lock ordering wrt do_page_fault's mmap_sem

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Fix inotify lock order reversal with mmap_sem due to holding locks over
copy_to_user.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Reported-by: "Daniel J Blueman" <daniel.blueman@gmail.com>
Tested-by: "Daniel J Blueman" <daniel.blueman@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2008-10-02 14:50:12 -07:00 committed by Linus Torvalds
parent 08650869e0
commit 16dbc6c961
2 changed files with 21 additions and 7 deletions
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27
fs/inotify_user.c
View file

@ -323,7 +323,7 @@ out:
}
/*
* remove_kevent - cleans up and ultimately frees the given kevent
* remove_kevent - cleans up the given kevent
*
* Caller must hold dev->ev_mutex.
*/
@ -334,7 +334,13 @@ static void remove_kevent(struct inotify_device *dev,
dev->event_count--;
dev->queue_size -= sizeof(struct inotify_event) + kevent->event.len;
}
/*
* free_kevent - frees the given kevent.
*/
static void free_kevent(struct inotify_kernel_event *kevent)
{
kfree(kevent->name);
kmem_cache_free(event_cachep, kevent);
}
@ -350,6 +356,7 @@ static void inotify_dev_event_dequeue(struct inotify_device *dev)
struct inotify_kernel_event *kevent;
kevent = inotify_dev_get_event(dev);
remove_kevent(dev, kevent);
free_kevent(kevent);
}
}
@ -433,17 +440,15 @@ static ssize_t inotify_read(struct file *file, char __user *buf,
dev = file->private_data;
while (1) {
int events;
prepare_to_wait(&dev->wq, &wait, TASK_INTERRUPTIBLE);
mutex_lock(&dev->ev_mutex);
events = !list_empty(&dev->events);
mutex_unlock(&dev->ev_mutex);
if (events) {
if (!list_empty(&dev->events)) {
ret = 0;
break;
}
mutex_unlock(&dev->ev_mutex);
if (file->f_flags & O_NONBLOCK) {
ret = -EAGAIN;
@ -462,7 +467,6 @@ static ssize_t inotify_read(struct file *file, char __user *buf,
if (ret)
return ret;
mutex_lock(&dev->ev_mutex);
while (1) {
struct inotify_kernel_event *kevent;
@ -481,6 +485,13 @@ static ssize_t inotify_read(struct file *file, char __user *buf,
}
break;
}
remove_kevent(dev, kevent);
/*
* Must perform the copy_to_user outside the mutex in order
* to avoid a lock order reversal with mmap_sem.
*/
mutex_unlock(&dev->ev_mutex);
if (copy_to_user(buf, &kevent->event, event_size)) {
ret = -EFAULT;
@ -498,7 +509,9 @@ static ssize_t inotify_read(struct file *file, char __user *buf,
count -= kevent->event.len;
}
remove_kevent(dev, kevent);
free_kevent(kevent);
mutex_lock(&dev->ev_mutex);
}
mutex_unlock(&dev->ev_mutex);

1
include/asm-x86/uaccess_64.h
View file

@ -7,6 +7,7 @@
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/prefetch.h>
#include <linux/lockdep.h>
#include <asm/page.h>
/*