Re: [PATCH] ocfs2: reduce ioctl stack usage

[Joseph Qi]

On 4/18/23 4:56 AM, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> On 32-bit architectures with KASAN_STACK enabled, the total stack usage
> of the ocfs2_ioctl function grows beyond the warning limit:
> 
> fs/ocfs2/ioctl.c: In function 'ocfs2_ioctl':
> fs/ocfs2/ioctl.c:934:1: error: the frame size of 1448 bytes is larger than 1400 bytes [-Werror=frame-larger-than=]
> 
> Move each of the variables into a basic block, and mark ocfs2_info_handle()
> as noinline_for_stack, in order to have the variable share stack slots.
> 
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

Looks good.

Reviewed-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>

> ---
>  fs/ocfs2/ioctl.c | 37 ++++++++++++++++++++++++++-----------
>  1 file changed, 26 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/ocfs2/ioctl.c b/fs/ocfs2/ioctl.c
> index 811a6ea374bb..b1550ba73f96 100644
> --- a/fs/ocfs2/ioctl.c
> +++ b/fs/ocfs2/ioctl.c
> @@ -803,8 +803,8 @@ static int ocfs2_get_request_ptr(struct ocfs2_info *info, int idx,
>   * a better backward&forward compatibility, since a small piece of
>   * request will be less likely to be broken if disk layout get changed.
>   */
> -static int ocfs2_info_handle(struct inode *inode, struct ocfs2_info *info,
> -			     int compat_flag)
> +static noinline_for_stack int
> +ocfs2_info_handle(struct inode *inode, struct ocfs2_info *info, int compat_flag)
>  {
>  	int i, status = 0;
>  	u64 req_addr;
> @@ -840,27 +840,26 @@ static int ocfs2_info_handle(struct inode *inode, struct ocfs2_info *info,
>  long ocfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  {
>  	struct inode *inode = file_inode(filp);
> -	int new_clusters;
> -	int status;
> -	struct ocfs2_space_resv sr;
> -	struct ocfs2_new_group_input input;
> -	struct reflink_arguments args;
> -	const char __user *old_path;
> -	const char __user *new_path;
> -	bool preserve;
> -	struct ocfs2_info info;
>  	void __user *argp = (void __user *)arg;
> +	int status;
>  
>  	switch (cmd) {
>  	case OCFS2_IOC_RESVSP:
>  	case OCFS2_IOC_RESVSP64:
>  	case OCFS2_IOC_UNRESVSP:
>  	case OCFS2_IOC_UNRESVSP64:
> +	{
> +		struct ocfs2_space_resv sr;
> +
>  		if (copy_from_user(&sr, (int __user *) arg, sizeof(sr)))
>  			return -EFAULT;
>  
>  		return ocfs2_change_file_space(filp, cmd, &sr);
> +	}
>  	case OCFS2_IOC_GROUP_EXTEND:
> +	{
> +		int new_clusters;
> +
>  		if (!capable(CAP_SYS_RESOURCE))
>  			return -EPERM;
>  
> @@ -873,8 +872,12 @@ long ocfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  		status = ocfs2_group_extend(inode, new_clusters);
>  		mnt_drop_write_file(filp);
>  		return status;
> +	}
>  	case OCFS2_IOC_GROUP_ADD:
>  	case OCFS2_IOC_GROUP_ADD64:
> +	{
> +		struct ocfs2_new_group_input input;
> +
>  		if (!capable(CAP_SYS_RESOURCE))
>  			return -EPERM;
>  
> @@ -887,7 +890,14 @@ long ocfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  		status = ocfs2_group_add(inode, &input);
>  		mnt_drop_write_file(filp);
>  		return status;
> +	}
>  	case OCFS2_IOC_REFLINK:
> +	{
> +		struct reflink_arguments args;
> +		const char __user *old_path;
> +		const char __user *new_path;
> +		bool preserve;
> +
>  		if (copy_from_user(&args, argp, sizeof(args)))
>  			return -EFAULT;
>  		old_path = (const char __user *)(unsigned long)args.old_path;
> @@ -895,11 +905,16 @@ long ocfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  		preserve = (args.preserve != 0);
>  
>  		return ocfs2_reflink_ioctl(inode, old_path, new_path, preserve);
> +	}
>  	case OCFS2_IOC_INFO:
> +	{
> +		struct ocfs2_info info;
> +
>  		if (copy_from_user(&info, argp, sizeof(struct ocfs2_info)))
>  			return -EFAULT;
>  
>  		return ocfs2_info_handle(inode, &info, 0);
> +	}
>  	case FITRIM:
>  	{
>  		struct super_block *sb = inode->i_sb;