2023-08-02 10:39:29

by Luis Henriques

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

If casefolding the filename fails, we'll be leaking fscrypt_buf name.
Make sure we free it in the error paths of ext4_fname_setup_filename() and
ext4_fname_prepare_lookup() functions.

Fixes: 1ae98e295fa2 ("ext4: optimize match for casefolded encrypted dirs")
Signed-off-by: Luís Henriques <[email protected]>
---
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..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,

#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,

#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;
}

2023-08-03 05:25:24

by Eric Biggers

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

On Wed, Aug 02, 2023 at 10:49:31AM +0100, Lu?s 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?

- Eric

2023-08-03 09:17:18

by Luis Henriques

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

Eric Biggers <[email protected]> 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