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-rw-r--r--fs/kernfs/file.c51
-rw-r--r--include/linux/kernfs.h1
2 files changed, 30 insertions, 22 deletions
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 7247252ee9b1..e1574008adc9 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -190,15 +190,16 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
char *buf;
buf = of->prealloc_buf;
- if (!buf)
+ if (buf)
+ mutex_lock(&of->prealloc_mutex);
+ else
buf = kmalloc(len, GFP_KERNEL);
if (!buf)
return -ENOMEM;
/*
* @of->mutex nests outside active ref and is used both to ensure that
- * the ops aren't called concurrently for the same open file, and
- * to provide exclusive access to ->prealloc_buf (when that exists).
+ * the ops aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!kernfs_get_active(of->kn)) {
@@ -214,21 +215,23 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
else
len = -EINVAL;
+ kernfs_put_active(of->kn);
+ mutex_unlock(&of->mutex);
+
if (len < 0)
- goto out_unlock;
+ goto out_free;
if (copy_to_user(user_buf, buf, len)) {
len = -EFAULT;
- goto out_unlock;
+ goto out_free;
}
*ppos += len;
- out_unlock:
- kernfs_put_active(of->kn);
- mutex_unlock(&of->mutex);
out_free:
- if (buf != of->prealloc_buf)
+ if (buf == of->prealloc_buf)
+ mutex_unlock(&of->prealloc_mutex);
+ else
kfree(buf);
return len;
}
@@ -284,15 +287,22 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
}
buf = of->prealloc_buf;
- if (!buf)
+ if (buf)
+ mutex_lock(&of->prealloc_mutex);
+ else
buf = kmalloc(len + 1, GFP_KERNEL);
if (!buf)
return -ENOMEM;
+ if (copy_from_user(buf, user_buf, len)) {
+ len = -EFAULT;
+ goto out_free;
+ }
+ buf[len] = '\0'; /* guarantee string termination */
+
/*
* @of->mutex nests outside active ref and is used both to ensure that
- * the ops aren't called concurrently for the same open file, and
- * to provide exclusive access to ->prealloc_buf (when that exists).
+ * the ops aren't called concurrently for the same open file.
*/
mutex_lock(&of->mutex);
if (!kernfs_get_active(of->kn)) {
@@ -301,26 +311,22 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
goto out_free;
}
- if (copy_from_user(buf, user_buf, len)) {
- len = -EFAULT;
- goto out_unlock;
- }
- buf[len] = '\0'; /* guarantee string termination */
-
ops = kernfs_ops(of->kn);
if (ops->write)
len = ops->write(of, buf, len, *ppos);
else
len = -EINVAL;
+ kernfs_put_active(of->kn);
+ mutex_unlock(&of->mutex);
+
if (len > 0)
*ppos += len;
-out_unlock:
- kernfs_put_active(of->kn);
- mutex_unlock(&of->mutex);
out_free:
- if (buf != of->prealloc_buf)
+ if (buf == of->prealloc_buf)
+ mutex_unlock(&of->prealloc_mutex);
+ else
kfree(buf);
return len;
}
@@ -687,6 +693,7 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
error = -ENOMEM;
if (!of->prealloc_buf)
goto err_free;
+ mutex_init(&of->prealloc_mutex);
}
/*
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index c06c44242f39..d306e282bb1d 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -177,6 +177,7 @@ struct kernfs_open_file {
/* private fields, do not use outside kernfs proper */
struct mutex mutex;
+ struct mutex prealloc_mutex;
int event;
struct list_head list;
char *prealloc_buf;