Messages in this thread | | | From | Nick Desaulniers <> | Date | Mon, 15 Jun 2020 11:23:44 -0700 | Subject | Re: [PATCH] security: fix the key_permission LSM hook function type |
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On Mon, Jun 15, 2020 at 11:21 AM Kees Cook <keescook@chromium.org> wrote: > > On Mon, Jun 15, 2020 at 11:12:32AM -0700, Sami Tolvanen wrote: > > Commit 8c0637e950d6 ("keys: Make the KEY_NEED_* perms an enum rather than > > a mask") changed the type of the key_permission callback functions, but > > didn't change the type of the hook, which trips indirect call checking with > > Control-Flow Integrity (CFI). This change fixes the issue by changing the > > hook type to match the functions. > > > > Fixes: 8c0637e950d6 ("keys: Make the KEY_NEED_* perms an enum rather than a mask") > > Signed-off-by: Sami Tolvanen <samitolvanen@google.com> > > Thanks for fixing this! > > Acked-by: Kees Cook <keescook@chromium.org> > > I wonder if there is any compiler option we can turn on to catch the > implicit enum/int casting that would help for these kinds of things > without absolutely exploding the build warnings. > > I see -Wenum-conversion, but that seems to be between enums, not between > int. > > I see this, but it's external: > https://noamlewis.wordpress.com/2017/10/05/type-safe-enums-in-c-using-a-clang-plugin/
Unfortunately, using a looser integral type is the typical workaround for -Wenum-conversion warnings (which is on by default, GCC recently added that flag, too). For warning on enum to int, the kernel would probably blow up with warnings. I don't know of any such existing warning flag.
> > -Kees > > > --- > > include/linux/lsm_hook_defs.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h > > index 6791813cd439..24f6683f1cfc 100644 > > --- a/include/linux/lsm_hook_defs.h > > +++ b/include/linux/lsm_hook_defs.h > > @@ -360,7 +360,7 @@ LSM_HOOK(int, 0, key_alloc, struct key *key, const struct cred *cred, > > unsigned long flags) > > LSM_HOOK(void, LSM_RET_VOID, key_free, struct key *key) > > LSM_HOOK(int, 0, key_permission, key_ref_t key_ref, const struct cred *cred, > > - unsigned perm) > > + enum key_need_perm need_perm) > > LSM_HOOK(int, 0, key_getsecurity, struct key *key, char **_buffer) > > #endif /* CONFIG_KEYS */ > > > > > > base-commit: b3a9e3b9622ae10064826dccb4f7a52bd88c7407 > > -- > > 2.27.0.290.gba653c62da-goog > > > > -- > Kees Cook > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/202006151113.7A2F638A7%40keescook.
-- Thanks, ~Nick Desaulniers
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