[PATCH] Btrfs: avoid stack bloat in btrfs_ioctl_fs_info()

[PATCH] Btrfs: avoid stack bloat in btrfs_ioctl_fs_info()

[Li Zefan]

The size of struct btrfs_ioctl_fs_info_args is as big as 1KB, so
don't declare the variable on stack.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 fs/btrfs/ioctl.c |   23 ++++++++++++++---------
 1 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index ac37040..9705c5c 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2054,29 +2054,34 @@ static long btrfs_ioctl_rm_dev(struct btrfs_root *root, void __user *arg)
 
 static long btrfs_ioctl_fs_info(struct btrfs_root *root, void __user *arg)
 {
-	struct btrfs_ioctl_fs_info_args fi_args;
+	struct btrfs_ioctl_fs_info_args *fi_args;
 	struct btrfs_device *device;
 	struct btrfs_device *next;
 	struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
+	int ret = 0;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	fi_args.num_devices = fs_devices->num_devices;
-	fi_args.max_id = 0;
-	memcpy(&fi_args.fsid, root->fs_info->fsid, sizeof(fi_args.fsid));
+	fi_args = kzalloc(sizeof(*fi_args), GFP_KERNEL);
+	if (!fi_args)
+		return -ENOMEM;
+
+	fi_args->num_devices = fs_devices->num_devices;
+	memcpy(&fi_args->fsid, root->fs_info->fsid, sizeof(fi_args->fsid));
 
 	mutex_lock(&fs_devices->device_list_mutex);
 	list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
-		if (device->devid > fi_args.max_id)
-			fi_args.max_id = device->devid;
+		if (device->devid > fi_args->max_id)
+			fi_args->max_id = device->devid;
 	}
 	mutex_unlock(&fs_devices->device_list_mutex);
 
-	if (copy_to_user(arg, &fi_args, sizeof(fi_args)))
-		return -EFAULT;
+	if (copy_to_user(arg, fi_args, sizeof(fi_args)))
+		ret = -EFAULT;
 
-	return 0;
+	kfree(fi_args);
+	return ret;
 }
 
 static long btrfs_ioctl_dev_info(struct btrfs_root *root, void __user *arg)
-- 1.7.3.1 

Re: [PATCH] Btrfs: avoid stack bloat in btrfs_ioctl_fs_info()

[Arne Jansen]

On 08.06.2011 05:58, Li Zefan wrote:
> The size of struct btrfs_ioctl_fs_info_args is as big as 1KB, so
> don't declare the variable on stack.
> 
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> ---
>  fs/btrfs/ioctl.c |   23 ++++++++++++++---------
>  1 files changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index ac37040..9705c5c 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -2054,29 +2054,34 @@ static long btrfs_ioctl_rm_dev(struct btrfs_root *root, void __user *arg)
>  
>  static long btrfs_ioctl_fs_info(struct btrfs_root *root, void __user *arg)
>  {
> -	struct btrfs_ioctl_fs_info_args fi_args;
> +	struct btrfs_ioctl_fs_info_args *fi_args;
>  	struct btrfs_device *device;
>  	struct btrfs_device *next;
>  	struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
> +	int ret = 0;
>  
>  	if (!capable(CAP_SYS_ADMIN))
>  		return -EPERM;
>  
> -	fi_args.num_devices = fs_devices->num_devices;
> -	fi_args.max_id = 0;
> -	memcpy(&fi_args.fsid, root->fs_info->fsid, sizeof(fi_args.fsid));
> +	fi_args = kzalloc(sizeof(*fi_args), GFP_KERNEL);
> +	if (!fi_args)
> +		return -ENOMEM;
> +
> +	fi_args->num_devices = fs_devices->num_devices;
> +	memcpy(&fi_args->fsid, root->fs_info->fsid, sizeof(fi_args->fsid));
>  
>  	mutex_lock(&fs_devices->device_list_mutex);
>  	list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
> -		if (device->devid > fi_args.max_id)
> -			fi_args.max_id = device->devid;
> +		if (device->devid > fi_args->max_id)
> +			fi_args->max_id = device->devid;
>  	}
>  	mutex_unlock(&fs_devices->device_list_mutex);
>  
> -	if (copy_to_user(arg, &fi_args, sizeof(fi_args)))
> -		return -EFAULT;
> +	if (copy_to_user(arg, fi_args, sizeof(fi_args)))

sizeof(*fi_args)

will integrate that, thanks :)

-Arne

> +		ret = -EFAULT;
>  
> -	return 0;
> +	kfree(fi_args);
> +	return ret;
>  }
>  
>  static long btrfs_ioctl_dev_info(struct btrfs_root *root, void __user *arg)
> -- 1.7.3.1 
> --
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Re: [PATCH] Btrfs: avoid stack bloat in btrfs_ioctl_fs_info()

[Li Zefan]

>> -	if (copy_to_user(arg, &fi_args, sizeof(fi_args)))
>> -		return -EFAULT;
>> +	if (copy_to_user(arg, fi_args, sizeof(fi_args)))
> 
> sizeof(*fi_args)
> 
> will integrate that, thanks :)
> 

Oops, what a silly mistake!