linux-kernel - Re: [PATCH] sysfs: Don't leak secdata when a sysfs

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Message-ID: <m1fx8uz7qs.fsf@fess.ebiederm.org>
Date:	Wed, 04 Nov 2009 06:26:19 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, sds@...ho.nsa.gov, jmorris@...ei.org,
	casey@...aufler-ca.com, linux-security-module@...r.kernel.org
Subject: Re: [PATCH] sysfs: Don't leak secdata when a sysfs_dirent is freed.

"Serge E. Hallyn" <serue@...ibm.com> writes:

> Quoting Eric W. Biederman (ebiederm@...ssion.com):
>> 
>> While refreshing my sysfs patches I noticed a leak in the secdata
>> implementation.  We don't free the secdata when we free the
>> sysfs dirent. 
>> 
>> This is a bug in 2.6.32-rc5 that we really should close.
>> 
>> Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
>
> I'm surprised no kmemleak or anything has found this - but I guess
> not many sites hand-set custom selinux contexts on sysfs?

I don't expect so since you couldn't customize it in 2.6.31.
This is brand new code, and this corner case was just overlooked
in the review.

Eric


> Acked-by: Serge Hallyn <serue@...ibm.com>
>
>> ---
>> 
>>  fs/sysfs/dir.c |    4 ++++
>>  1 files changed, 4 insertions(+), 0 deletions(-)
>> 
>> diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
>> index 5fad489..e020183 100644
>> --- a/fs/sysfs/dir.c
>> +++ b/fs/sysfs/dir.c
>> @@ -21,6 +21,7 @@
>>  #include <linux/completion.h>
>>  #include <linux/mutex.h>
>>  #include <linux/slab.h>
>> +#include <linux/security.h>
>>  #include "sysfs.h"
>> 
>>  DEFINE_MUTEX(sysfs_mutex);
>> @@ -285,6 +286,9 @@ void release_sysfs_dirent(struct sysfs_dirent * sd)
>>  		sysfs_put(sd->s_symlink.target_sd);
>>  	if (sysfs_type(sd) & SYSFS_COPY_NAME)
>>  		kfree(sd->s_name);
>> +	if (sd->s_iattr && sd->s_iattr->ia_secdata)
>> +		security_release_secctx(sd->s_iattr->ia_secdata,
>> +					sd->s_iattr->ia_secdata_len);
>>  	kfree(sd->s_iattr);
>>  	sysfs_free_ino(sd->s_ino);
>>  	kmem_cache_free(sysfs_dir_cachep, sd);
>> -- 
>> 1.6.5.2.143.g8cc62
>> 
>> --
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