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

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Message-ID: <20250314164708.GA1542@breakpoint.cc>
Date: Fri, 14 Mar 2025 17:47:08 +0100
From: Florian Westphal <fw@...len.de>
To: Casey Schaufler <casey@...aufler-ca.com>
Cc: Florian Westphal <fw@...len.de>, Chenyuan Yang <chenyuan0y@...il.com>,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: Initialize ctx to avoid memory allocation error

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.