Re: [f2fs-dev] [PATCH v3 2/2] f2fs: fix compat F2FS_IOC_{MOVE, GARBAGE_COLLECT}_RANGE

[Eric Biggers]

This patch is marked 2/2, but it seems you sent it out on its own.  Patch series
are supposed to be resend in full; otherwise people can see just one patch and
have no context.

On Thu, Nov 05, 2020 at 09:09:34AM +0800, Chao Yu wrote:
> Eric reported a ioctl bug in below link:
> 
> https://lore.kernel.org/linux-f2fs-devel/20201103032234.GB2875@sol.localdomain/
> 
> That said, on some 32-bit architectures, u64 has only 32-bit alignment,
> notably i386 and x86_32, so that size of struct f2fs_gc_range compiled
> in x86_32 is 20 bytes, however the size in x86_64 is 24 bytes, binary
> compiled in x86_32 can not call F2FS_IOC_GARBAGE_COLLECT_RANGE successfully
> due to mismatched value of ioctl command in between binary and f2fs
> module, similarly, F2FS_IOC_MOVE_RANGE will fail too.
> 
> In this patch we introduce two ioctls for compatibility of above special
> 32-bit binary:
> - F2FS_IOC32_GARBAGE_COLLECT_RANGE
> - F2FS_IOC32_MOVE_RANGE
> 

It would be good to add a proper reported-by line, otherwise it's not clear who
"Eric" is (there are lots of Erics):

Reported-by: Eric Biggers <ebiggers@xxxxxxxxxx>

> +static int __f2fs_ioc_gc_range(struct file *filp, struct f2fs_gc_range *range)
>  {
> -	struct inode *inode = file_inode(filp);
> -	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> -	struct f2fs_gc_range range;
> +	struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(filp));
>  	u64 end;
>  	int ret;
>  
> +	if (unlikely(f2fs_cp_error(sbi)))
> +		return -EIO;
> +	if (!f2fs_is_checkpoint_ready(sbi))
> +		return -ENOSPC;

These two checkpoint-related checks weren't present in the original version.
Is that intentional?

> +static int __f2fs_ioc_move_range(struct file *filp,
> +				struct f2fs_move_range *range)
>  {
> -	struct f2fs_move_range range;
> +	struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(filp));
>  	struct fd dst;
>  	int err;
>  
> +	if (unlikely(f2fs_cp_error(sbi)))
> +		return -EIO;
> +	if (!f2fs_is_checkpoint_ready(sbi))
> +		return -ENOSPC;
> +

Likewise here.

> diff --git a/include/uapi/linux/f2fs.h b/include/uapi/linux/f2fs.h
> index f00199a2e38b..8c14e88a9645 100644
> --- a/include/uapi/linux/f2fs.h
> +++ b/include/uapi/linux/f2fs.h
> @@ -5,6 +5,10 @@
>  #include <linux/types.h>
>  #include <linux/ioctl.h>
>  
> +#ifdef __KERNEL__
> +#include <linux/compat.h>
> +#endif
> +
>  /*
>   * f2fs-specific ioctl commands
>   */
> @@ -65,6 +69,16 @@ struct f2fs_gc_range {
>  	__u64 len;
>  };
>  
> +#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
> +struct compat_f2fs_gc_range {
> +	u32 sync;
> +	compat_u64 start;
> +	compat_u64 len;
> +};
> +#define F2FS_IOC32_GARBAGE_COLLECT_RANGE	_IOW(F2FS_IOCTL_MAGIC, 11,\
> +						struct compat_f2fs_gc_range)
> +#endif
> +
>  struct f2fs_defragment {
>  	__u64 start;
>  	__u64 len;
> @@ -77,6 +91,17 @@ struct f2fs_move_range {
>  	__u64 len;		/* size to move */
>  };
>  
> +#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
> +struct compat_f2fs_move_range {
> +	u32 dst_fd;
> +	compat_u64 pos_in;
> +	compat_u64 pos_out;
> +	compat_u64 len;
> +};
> +#define F2FS_IOC32_MOVE_RANGE		_IOWR(F2FS_IOCTL_MAGIC, 9,	\
> +					struct compat_f2fs_move_range)
> +#endif
> +
>  struct f2fs_flush_device {
>  	__u32 dev_num;		/* device number to flush */
>  	__u32 segments;		/* # of segments to flush */
> -- 

Did you consider instead putting these compat definitions in an internal kernel
header, or even just in the .c file, to avoid cluttering up the UAPI header?

- Eric