Re: [PATCH v2] ext4: fix memory leaks in ext4_fname_{setup_filename,prepare_lookup}

Luís Henriques
2023-08-03T08:58:33Z

Eric Biggers <ebiggers@kernel.org> writes:

> On Wed, Aug 02, 2023 at 10:49:31AM +0100, Luís Henriques wrote:
>> If casefolding the filename fails, we'll be leaking fscrypt_buf name.
>
> fscrypt_buf => fscrypt_name
>
>> diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
>> index e20ac0654b3f..3c05c7f3415b 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,
>> struct fscrypt_name name;
>> int err;
>>
>> err = fscrypt_setup_filename(dir, iname, lookup, &name);
>> if (err)
>> return err;
>>
>> ext4_fname_from_fscrypt_name(fname, &name);
>>
>> #if IS_ENABLED(CONFIG_UNICODE)
>> err = ext4_fname_setup_ci_filename(dir, iname, fname);
>> + if (err)
>> + fscrypt_free_filename(&name);
>> #endif
>> return err;
>> }
>> @@ -51,6 +53,8 @@ int ext4_fname_prepare_lookup(struct inode *dir, struct dentry *dentry,
>> struct fscrypt_name name;
>> int err;
>>
>> err = fscrypt_prepare_lookup(dir, dentry, &name);
>> if (err)
>> return err;
>>
>> ext4_fname_from_fscrypt_name(fname, &name);
>>
>> #if IS_ENABLED(CONFIG_UNICODE)
>> err = ext4_fname_setup_ci_filename(dir, &dentry->d_name, fname);
>> + if (err)
>> + fscrypt_free_filename(&name);
>> #endif
>> return err;
>> }
>
> This works, but it's a bit weird that the freeing happens on the original struct
> fscrypt_name after it has already been "moved" to the struct ext4_filename by
> ext4_fname_from_fscrypt_name(). That leaves a dangling pointer in the struct
> ext4_filename. Maybe you should call ext4_fname_free_filename() instead, even
> though it would do some unnecessary work?

That makes sense, specially because fname is a parameter and it's probably
a good idea to clean-up everything before returning an error. Thanks.

Cheers,
--
Luís