linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadlock

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Date:   Fri, 16 Dec 2022 12:42:02 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     jaegeuk@...nel.org,
        syzbot+4793f6096d174c90b4f7@...kaller.appspotmail.com,
        linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadlock

On Fri, Dec 16, 2022 at 11:50:00PM +0800, Chao Yu wrote:
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index cad4bdd6f097..4bc98dbe8292 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -2336,6 +2336,7 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
>  {
>  	struct inode *inode = file_inode(filp);
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> +	u8 encrypt_pw_salt[16];
>  	int err;
>  
>  	if (!f2fs_sb_has_encrypt(sbi))
> @@ -2360,12 +2361,14 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
>  		goto out_err;
>  	}
>  got_it:
> -	if (copy_to_user((__u8 __user *)arg, sbi->raw_super->encrypt_pw_salt,
> -									16))
> -		err = -EFAULT;
> +	memcpy(encrypt_pw_salt, sbi->raw_super->encrypt_pw_salt, 16);
>  out_err:
>  	f2fs_up_write(&sbi->sb_lock);
>  	mnt_drop_write_file(filp);
> +
> +	if (!err && copy_to_user((__u8 __user *)arg, encrypt_pw_salt, 16))
> +		err = -EFAULT;
> +
>  	return err;

Reviewed-by: Eric Biggers <ebiggers@...gle.com>

- Eric