linux-kernel - Re: [PATCH] net: Initialize ctx to avoid memory allocation error

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Message-ID: <d2019823-4500-499a-8368-76c50a582f47@schaufler-ca.com>
Date: Fri, 14 Mar 2025 10:26:34 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Florian Westphal <fw@...len.de>
Cc: Chenyuan Yang <chenyuan0y@...il.com>, netfilter-devel@...r.kernel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH] net: Initialize ctx to avoid memory allocation error


On 3/14/2025 9:47 AM, Florian Westphal wrote:
> Casey Schaufler <casey@...aufler-ca.com> wrote:
>> If seclen is 0 it implies that there is no security context and that
>> the secctx is NULL. How that is handled in the release function is up
>> to the LSM. SELinux allocates secctx data, while Smack points to an
>> entry in a persistent table.
>>
>>> seclen needs to be > 0 or no secinfo is passed to userland,
>>> yet the secctx release function is called anyway.
>> That is correct. The security module is responsible for handling
>> the release of secctx correctly.
>>
>>> Should seclen be initialised to -1?  Or we need the change below too?
>> No. The security modules handle secctx their own way.
> Well, as-is security_release_secctx() can be called with garbage ctx;
> seclen is inited to 0, but ctx is not initialized unconditionally.

Which isn't an issue for any existing security module.