Re: [PATCH v3 2/5] fs: Check if utf8 encoding is loaded before calling utf8_unload()

From: Gabriel Krisman Bertazi <krisman@collabora.com>
To: Shreeya Patel <shreeya.patel@collabora.com>
Cc: tytso@mit.edu, adilger.kernel@dilger.ca, jaegeuk@kernel.org,
	chao@kernel.org, ebiggers@google.com, drosen@google.com,
	ebiggers@kernel.org, yuchao0@huawei.com,
	linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-fsdevel@vger.kernel.org, kernel@collabora.com,
	andre.almeida@collabora.com
Subject: Re: [PATCH v3 2/5] fs: Check if utf8 encoding is loaded before calling utf8_unload()
Date: Tue, 23 Mar 2021 15:10:40 -0400	[thread overview]
Message-ID: <87sg4ld6tr.fsf@collabora.com> (raw)
In-Reply-To: <20210323183201.812944-3-shreeya.patel@collabora.com> (Shreeya Patel's message of "Wed, 24 Mar 2021 00:01:58 +0530")

Shreeya Patel <shreeya.patel@collabora.com> writes:

> utf8_unload is being called if CONFIG_UNICODE is enabled.
> The ifdef block doesn't check if utf8 encoding has been loaded
> or not before calling the utf8_unload() function.
> This is not the expected behavior since it would sometimes lead
> to unloading utf8 even before loading it.
> Hence, add a condition which will check if sb->encoding is NOT NULL
> before calling the utf8_unload().

Just to mention this used to be safe, since it was just doing a
kfree(NULL), but won't be anymore after the rest of this series.

Reviewed-by: Gabriel Krisman Bertazi <krisman@collabora.com>

>
> Signed-off-by: Shreeya Patel <shreeya.patel@collabora.com>
> ---
>
> Changes in v3
>   - Add this patch to the series which checks if utf8 encoding
>     was loaded before calling uft8_unload().
>  
>  fs/ext4/super.c | 6 ++++--
>  fs/f2fs/super.c | 9 ++++++---
>  2 files changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index ad34a3727..e438d14f9 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1259,7 +1259,8 @@ static void ext4_put_super(struct super_block *sb)
>  	fs_put_dax(sbi->s_daxdev);
>  	fscrypt_free_dummy_policy(&sbi->s_dummy_enc_policy);
>  #ifdef CONFIG_UNICODE
> -	utf8_unload(sb->s_encoding);
> +	if (sb->s_encoding)
> +		utf8_unload(sb->s_encoding);
>  #endif
>  	kfree(sbi);
>  }
> @@ -5165,7 +5166,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  		crypto_free_shash(sbi->s_chksum_driver);
>  
>  #ifdef CONFIG_UNICODE
> -	utf8_unload(sb->s_encoding);
> +	if (sb->s_encoding)
> +		utf8_unload(sb->s_encoding);
>  #endif
>  
>  #ifdef CONFIG_QUOTA
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 706979375..0a04983c2 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -1430,7 +1430,8 @@ static void f2fs_put_super(struct super_block *sb)
>  	for (i = 0; i < NR_PAGE_TYPE; i++)
>  		kvfree(sbi->write_io[i]);
>  #ifdef CONFIG_UNICODE
> -	utf8_unload(sb->s_encoding);
> +	if (sb->s_encoding)
> +		utf8_unload(sb->s_encoding);
>  #endif
>  	kfree(sbi);
>  }
> @@ -4073,8 +4074,10 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>  		kvfree(sbi->write_io[i]);
>  
>  #ifdef CONFIG_UNICODE
> -	utf8_unload(sb->s_encoding);
> -	sb->s_encoding = NULL;
> +	if (sb->s_encoding) {
> +		utf8_unload(sb->s_encoding);
> +		sb->s_encoding = NULL;
> +	}
>  #endif
>  free_options:
>  #ifdef CONFIG_QUOTA

-- 
Gabriel Krisman Bertazi