On 10/24/2023 6:43 PM, Paul Moore wrote: > On Tue, Oct 24, 2023 at 6:23 PM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: >> On 10/24/2023 2:35 PM, Paul Moore wrote: >>> Zero out all of the size counters in the -E2BIG case (buffer too >>> small) to help make the current code a bit more robust in the face of >>> future code changes. >> I don't see how this change would have the described effect. >> What it looks like it would do is change the return from -E2BIG >> to 0, which would not have the desired result. > When @toobig is true, which it will be when one of the individual LSMs > return -E2BIG, the return value of security_getselfattr() is fixed to > -E2BIG (check the if-statements at the end of the function). Setting > @rc to zero as in this patch simply preserves some sanity in the > @count variable as we are no longer subtracting the E2BIG errno from > the @count value. Granted, in the @toobig case, @count doesn't do > anything meaningful, but I believe this does harden the code against > future changes. > > Look at the discussion between Mickaël and I in the v15 04/11 patch > for more background. > > https://lore.kernel.org/linux-security-module/20230912205658.3432-5-casey@xxxxxxxxxxxxxxxx OK. My bad for not looking beyond the patch. Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx> > >>> Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx> >>> --- >>> security/security.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/security/security.c b/security/security.c >>> index 988483fcf153..9c63acded4ee 100644 >>> --- a/security/security.c >>> +++ b/security/security.c >>> @@ -3951,8 +3951,9 @@ int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, >>> continue; >>> } >>> if (rc == -E2BIG) { >>> - toobig = true; >>> + rc = 0; >>> left = 0; >>> + toobig = true; >>> } else if (rc < 0) >>> return rc; >>> else
