Re: [PATCH v3] ext4: fix memory leaks in ext4_fname_{setup_filename,prepare_lookup}

[Eric Biggers]

On Thu, Aug 03, 2023 at 10:17:13AM +0100, Luís Henriques wrote:
> If the filename casefolding fails, we'll be leaking memory from the
> fscrypt_name struct, namely from the 'crypto_buf.name' member.
> 
> Make sure we free it in the error path on both ext4_fname_setup_filename()
> and ext4_fname_prepare_lookup() functions.
> 
> Fixes: 1ae98e295fa2 ("ext4: optimize match for casefolded encrypted dirs")
> Signed-off-by: Luís Henriques <lhenriques@xxxxxxx>
> ---
> Changes since v2:
> - Rephrased commit log to (hopefully!) make it more clear.
> - Use ext4_fname_free_filename() instead of fscrypt_free_filename().
>   Although not strictly needed, it cleans up the fname struct, removing a
>   dangling pointer to freed memory.
> 
> Changes since v1:
> - Include fix to ext4_fname_prepare_lookup() as well
> - Add 'Fixes:' tag
> 
>  fs/ext4/crypto.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
> index e20ac0654b3f..453d4da5de52 100644
> --- a/fs/ext4/crypto.c
> +++ b/fs/ext4/crypto.c
> @@ -33,6 +33,8 @@ int ext4_fname_setup_filename(struct inode *dir, const struct qstr *iname,
>  
>  #if IS_ENABLED(CONFIG_UNICODE)
>  	err = ext4_fname_setup_ci_filename(dir, iname, fname);
> +	if (err)
> +		ext4_fname_free_filename(fname);
>  #endif
>  	return err;
>  }
> @@ -51,6 +53,8 @@ int ext4_fname_prepare_lookup(struct inode *dir, struct dentry *dentry,
>  
>  #if IS_ENABLED(CONFIG_UNICODE)
>  	err = ext4_fname_setup_ci_filename(dir, &dentry->d_name, fname);
> +	if (err)
> +		ext4_fname_free_filename(fname);
>  #endif
>  	return err;
>  }

Reviewed-by: Eric Biggers <ebiggers@xxxxxxxxxx>

- Eric