On Tue, Nov 15, 2022 at 12:58 PM Roberto Sassu <roberto.sassu@xxxxxxxxxxxxxxx> wrote: > > From: Roberto Sassu <roberto.sassu@xxxxxxxxxx> > > LSMs should not be able to return arbitrary return values, as the callers > of the LSM infrastructure might not be ready to handle unexpected values > (e.g. positive values that are first converted to a pointer with ERR_PTR, > and then evaluated with IS_ERR()). > > Modify call_int_hook() to call is_ret_value_allowed(), so that the return > value from each LSM for a given hook is checked. If for the interval the > return value falls into the corresponding flag is not set, change the > return value to the default value, just for the current LSM. > > A misbehaving LSM would not have impact on the decision of other LSMs, as > the loop terminates whenever the return value is not zero. > > Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx> > --- > security/security.c | 34 ++++++++++++++++++++++++++++++++++ > 1 file changed, 34 insertions(+) Casey touched on some of this in his reply to patch 0/4, but basically I see this as a BPF LSM specific problem and not a generalized LSM issue that should be addressed at the LSM layer. Especially if the solution involves incurring additional processing for every LSM hook instantiation, regardless if a BPF LSM is present. Reading your overall patchset description I believe that you understand this too. If you want to somehow instrument the LSM hook definitions (what I believe to be the motivation behind patch 3/4) to indicate valid return values for use by the BPF verifier, I think we could entertain that, or at least discuss it further, but I'm not inclined to support any runtime overhead at the LSM layer for a specific LSM. -- paul-moore.com
