On Oct 14, 2024 Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote:
>
> Verify that the LSM releasing the secctx is the LSM that
> allocated it. This was not necessary when only one LSM could
> create a secctx, but once there can be more than one it is.
>
> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> ---
> security/apparmor/secid.c | 10 ++--------
> security/selinux/hooks.c | 10 ++--------
> 2 files changed, 4 insertions(+), 16 deletions(-)
>
> diff --git a/security/apparmor/secid.c b/security/apparmor/secid.c
> index 5d92fc3ab8b4..974f802cbe5a 100644
> --- a/security/apparmor/secid.c
> +++ b/security/apparmor/secid.c
> @@ -122,14 +122,8 @@ int apparmor_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid)
>
> void apparmor_release_secctx(struct lsm_context *cp)
> {
> - /*
> - * stacking scaffolding:
> - * When it is possible for more than one LSM to provide a
> - * release hook, do this check:
> - * if (cp->id == LSM_ID_APPARMOR || cp->id == LSM_ID_UNDEF)
> - */
> -
> - kfree(cp->context);
> + if (cp->id == LSM_ID_APPARMOR)
> + kfree(cp->context);
Should we set cp->context to NULL too? One could argue that it's an
unecessary assignment, given the cp->id checks, and they wouldn't be
wrong, but considering the potential for a BPF LSM to do things with
a lsm_context, I wonder if resetting the pointer to NULL is the
smart thing to do.
This obviously applies to the SELinux code (below) too.
> }
>
> /**
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 79776a5e651d..b9286c2c5efe 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -6640,14 +6640,8 @@ static int selinux_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid)
>
> static void selinux_release_secctx(struct lsm_context *cp)
> {
> - /*
> - * stacking scaffolding:
> - * When it is possible for more than one LSM to provide a
> - * release hook, do this check:
> - * if (cp->id == LSM_ID_SELINUX || cp->id == LSM_ID_UNDEF)
> - */
> -
> - kfree(cp->context);
> + if (cp->id == LSM_ID_SELINUX)
> + kfree(cp->context);
> }
>
> static void selinux_inode_invalidate_secctx(struct inode *inode)
--
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