On Mon, Oct 21, 2024 at 8:06 PM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: > On 10/21/2024 4:39 PM, Paul Moore wrote: > > 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. > > Wouldn't hurt. I'll go ahead and add that. If a BPF LSM does anything > with a lsm_context we're likely to hear about the many issues quite > quickly. Yes, I suspect you're right about that, at least we can protect against a UAF in this one case :) -- paul-moore.com