linux-kernel - Re: [PATCH v2 1/6] LSM: Ensure the correct LSM context releaser

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Message-ID: <bab1de2e-0205-40dd-af3e-5956ff349948@schaufler-ca.com>
Date: Mon, 21 Oct 2024 16:58:08 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Paul Moore <paul@...l-moore.com>, linux-security-module@...r.kernel.org
Cc: jmorris@...ei.org, serge@...lyn.com, keescook@...omium.org,
 john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp,
 stephen.smalley.work@...il.com, linux-kernel@...r.kernel.org,
 selinux@...r.kernel.org, mic@...ikod.net, linux-integrity@...r.kernel.org,
 netdev@...r.kernel.org, audit@...r.kernel.org,
 netfilter-devel@...r.kernel.org, linux-nfs@...r.kernel.org,
 Todd Kjos <tkjos@...gle.com>, Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v2 1/6] LSM: Ensure the correct LSM context releaser

On 10/21/2024 4:39 PM, Paul Moore wrote:
> On Oct 14, 2024 Casey Schaufler <casey@...aufler-ca.com> wrote:
>> Add a new lsm_context data structure to hold all the information about a
>> "security context", including the string, its size and which LSM allocated
>> the string. The allocation information is necessary because LSMs have
>> different policies regarding the lifecycle of these strings. SELinux
>> allocates and destroys them on each use, whereas Smack provides a pointer
>> to an entry in a list that never goes away.
>>
>> Update security_release_secctx() to use the lsm_context instead of a
>> (char *, len) pair. Change its callers to do likewise.  The LSMs
>> supporting this hook have had comments added to remind the developer
>> that there is more work to be done.
>>
>> The BPF security module provides all LSM hooks. While there has yet to
>> be a known instance of a BPF configuration that uses security contexts,
>> the possibility is real. In the existing implementation there is
>> potential for multiple frees in that case.
>>
>> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
>> Cc: linux-integrity@...r.kernel.org
>> Cc: netdev@...r.kernel.org
>> Cc: audit@...r.kernel.org
>> Cc: netfilter-devel@...r.kernel.org
>> To: Pablo Neira Ayuso <pablo@...filter.org>
>> Cc: linux-nfs@...r.kernel.org
>> Cc: Todd Kjos <tkjos@...gle.com>
>> Reviewed-by: Serge Hallyn <sergeh@...nel.org>
>> ---
>>  drivers/android/binder.c                | 24 ++++++-------
>>  fs/ceph/xattr.c                         |  6 +++-
>>  fs/nfs/nfs4proc.c                       |  8 +++--
>>  fs/nfsd/nfs4xdr.c                       |  8 +++--
>>  include/linux/lsm_hook_defs.h           |  2 +-
>>  include/linux/security.h                | 35 +++++++++++++++++--
>>  include/net/scm.h                       | 11 +++---
>>  kernel/audit.c                          | 30 ++++++++---------
>>  kernel/auditsc.c                        | 23 +++++++------
>>  net/ipv4/ip_sockglue.c                  | 10 +++---
>>  net/netfilter/nf_conntrack_netlink.c    | 10 +++---
>>  net/netfilter/nf_conntrack_standalone.c |  9 +++--
>>  net/netfilter/nfnetlink_queue.c         | 13 ++++---
>>  net/netlabel/netlabel_unlabeled.c       | 45 +++++++++++--------------
>>  net/netlabel/netlabel_user.c            | 11 +++---
>>  security/apparmor/include/secid.h       |  2 +-
>>  security/apparmor/secid.c               | 11 ++++--
>>  security/security.c                     |  8 ++---
>>  security/selinux/hooks.c                | 11 ++++--
>>  19 files changed, 167 insertions(+), 110 deletions(-)
> ..
>
>> diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
>> index 1bc2d0890a9f..8303bbcfc543 100644
>> --- a/net/netlabel/netlabel_unlabeled.c
>> +++ b/net/netlabel/netlabel_unlabeled.c
>> @@ -1127,14 +1122,14 @@ static int netlbl_unlabel_staticlist_gen(u32 cmd,
>>  		secid = addr6->secid;
>>  	}
>>  
>> -	ret_val = security_secid_to_secctx(secid, &secctx, &secctx_len);
>> +	ret_val = security_secid_to_secctx(secid, &ctx.context, &ctx.len);
>>  	if (ret_val != 0)
>>  		goto list_cb_failure;
>>  	ret_val = nla_put(cb_arg->skb,
>>  			  NLBL_UNLABEL_A_SECCTX,
>> -			  secctx_len,
>> -			  secctx);
>> -	security_release_secctx(secctx, secctx_len);
>> +			  ctx.len,
>> +			  ctx.context);
> Nitpicky alignment issue; please keep the arguments aligned as they
> are currently.

Not a problem, although it looks like it's correct to me. I'll check to make sure.

>
>> +	security_release_secctx(&ctx);
>>  	if (ret_val != 0)
>>  		goto list_cb_failure;
>>  
> --
> paul-moore.com
>